Variable valve timing control device of internal combustion engine

ABSTRACT

A required valve timing change rate Vreq is calculated so as to make a deviation D between a target valve timing VTtg and an actual valve timing VT small and then a required speed difference DMCRreq between a motor  26  and a camshaft  16  is calculated on a basis of the required valve timing change rate Vreq. When the deviation D is larger than a predetermined value, a required motor speed Rmreq is calculated by adding the required speed difference DMCRreq to a camshaft speed RC and a motor control value is calculated so as to control the motor speed RM to the required motor speed Rmreq. When the deviation D is not larger than the predetermined value, the camshaft speed RC is set as the required motor speed Rmreq and the motor control value is calculated so as to control the motor speed RM to the camshaft speed RC.

TECHNICAL FIELD

This invention relates to a variable valve timing control device of aninternal combustion engine, for varying the valve timing of intakevalves or exhaust valves of an internal combustion engine.

BACKGROUND ART

In recent years, among internal combustion engines mounted in automotivevehicles, an increasing number have employed variable valve timingdevices for varying the valve timing of intake valves and exhaust valveswith the object of increasing output, reducing fuel consumption, andlowering exhaust emissions. Most variable valve timing devices in use atpresent change the valve timing of intake valves and/or exhaust valvesdriven to open and close by a camshaft by driving a phase-varyingmechanism with hydraulic pressure to vary the rotation phase of thecamshaft with respect to a crankshaft. However, in a hydraulicallydriven variable valve timing device like this there is the shortcomingthat in cold conditions and on starting of the engine the hydraulicpressure is insufficient, the responsiveness of hydraulic control falls,and the accuracy of valve timing control falls.

In this connection, as disclosed for example in JP-A-6-213021,motor-driven variable valve timing devices have been developed, in whicha phase-varying mechanism is driven with drive power from a motor tovary the rotation phase of a camshaft with respect to a crankshaft andthereby vary a valve timing.

However, in this motor-driven variable valve timing device of relatedart, because the construction is such that the motor as a whole rotatesintegrally with a pulley rotationally driven by the crankshaft, there isthe shortcoming that the inertial weight of the rotating system of thevariable valve timing device is heavy and the durability of the variablevalve timing device is poor. Furthermore, a sliding contact arrangementusing brushes or the like has to be used to connect the rotating motorwith external electrical wiring, and this also constitutes a cause ofreduced durability. Also, motor-driven variable valve timing devices ofrelated art have had the shortcoming that their overall construction iscomplex and they are high in cost.

The present invention was made in view of these circumstances, and anobject of the invention is to provide a variable valve timing controldevice of an internal combustion engine with which while fulfilling therequirements of increased durability and reduced cost of a variablevalve timing device it is possible to control a valve timing by motordrive and it is possible to raise the accuracy of valve timing control.

DISCLOSURE OF THE INVENTION

To achieve the above-mentioned object, a variable valve timing deviceaccording to the invention has a first rotating member disposedconcentrically with a camshaft and rotationally driven by rotary drivepower from a crankshaft; a second rotating member that rotatesintegrally with the camshaft; a phase-varying member that transmitsrotary power from the first rotating member to the second rotatingmember and varies the rotation phase of the second rotating member withrespect to the first rotating member; and a motor disposedconcentrically with the camshaft so as to control the rotation phase ofthis phase-varying member, and is constructed so that when the valvetiming is not to be changed the speed of the motor is matched to thespeed of the camshaft to match the turning speed of the phase-varyingmember to the speed of the camshaft and thereby hold the difference inrotation phase between the first rotating member and the second rotatingmember steady and thus hold the camshaft phase steady, and when thevalve timing is to be changed the speed of the motor is changed withrespect to the speed of the camshaft to change the turning speed of thephase-varying member with respect to the speed of the camshaft andthereby vary the difference in rotation phase between the first rotatingmember and the second rotating member and thus vary the camshaft phase.

In this construction, because it is not necessary for the whole motor tobe rotated, the inertial weight of the rotating system of the variablevalve timing device can be lightened and the motor can be directlyconnected to external electrical wiring by fixed connection means, andoverall the durability of the variable valve timing device can beincreased. Furthermore, the construction of the variable valve timingdevice is relatively simple, and the requirements of cost minimizationcan also be satisfied.

Also, in this invention, a required valve timing change rate iscalculated on the basis of a deviation between a target valve timing andan actual valve timing, a required speed difference between the motorand the camshaft is calculated on the basis of this required valvetiming change rate, and a motor control value is calculated so as tocontrol the speed difference between the motor and the camshaft to therequired speed difference. If this is done, the speed of the motor canbe feed-forwardly controlled with good accuracy so as to make the speeddifference between the motor and the camshaft match the required speeddifference, the actual valve timing can be controlled to the targetvalve timing by motor drive, and valve timing control accuracy can beimproved.

In this case, as the specific method for calculating the motor controlvalue needed for controlling the speed difference between the motor andthe camshaft to the required speed difference, for example a requiredmotor speed may be calculated on the basis of the camshaft speed and therequired speed difference and then a motor control value may becalculated so as to control the motor speed to the required motor speed.Or, a basic control value for controlling the motor speed to a basicmotor speed the same as the camshaft speed may be calculated, a changecontrol value for changing the motor speed by the required speeddifference with respect to the basic motor speed then calculated, and amotor control value then calculated on the basis of the basic controlvalue and the change control value. By using either of these methods itis possible to accurately calculate a motor control value needed tocontrol the speed difference between the motor and the camshaft to therequired speed difference.

Also, when the deviation between the target valve timing and the actualvalve timing is below a predetermined value, a motor control value maybe calculated so as to control the motor speed to the same speed as thecamshaft speed. If this is done, when the actual valve timing is at ornear the target valve timing, the actual valve timing can be held stablyas it is.

Now, because the output torque of the motor is also consumed as losstorque resulting from frictional losses in the variable valve timingdevice and drive losses on the camshaft side, the motor control value(applied voltage value, duty value or the like) needed to control thespeed difference between the motor and the camshaft to the requiredspeed difference varies with the drive losses in the variable valvetiming device and on the camshaft side. And because when the motorrotates a counter-electromotive force arises in the motor, the motorcontrol value needed to control the speed difference between the motorand the camshaft to the required speed difference also changes with thiscounter-electromotive force of the motor.

In view of these circumstances, preferably, a motor control value iscalculated using at least one among the frictional loss in the variablevalve timing device or a parameter correlated with this, the drive losson the camshaft side or a parameter correlated with this, and thecounter-electromotive force of the motor or a parameter correlated withthis. When this is done, because the motor control value can becalculated taking into account changes in drive losses in the variablevalve timing device and on the camshaft side and changes in thecounter-electromotive force of the motor, the motor control value neededto control the speed difference between the motor and the camshaft to arequired speed difference can be calculated with good accuracy withoutinfluences of frictional losses and counter-electromotive force beingsuffered.

In the variable valve timing device of this invention, because the valvetiming change rate changes in correspondence with the speed differencebetween the motor and the camshaft, the frictional loss in the variablevalve timing device changes in correspondence with the speed differencebetween the motor and the camshaft. Therefore when a parameter offrictional loss in the variable valve timing device (the frictional lossor a parameter correlated with this) is used, although the parameter offrictional loss in the variable valve timing device can be calculated incorrespondence with the actual speed difference between the motor andthe camshaft, alternatively the parameter of frictional loss in thevariable valve timing device may be calculated in correspondence withthe required speed difference between the motor and the camshaft. Inthis way it is possible to calculate feed-forwardly a parameter offrictional loss in the variable valve timing device to be used in thecalculation of the motor control value, and the responsiveness of motorrotation control can be increased. As a result, even under runningconditions in which the engine speed (the camshaft speed) changessuddenly, such as during racing (engine racing), the motor rotationspeed can be made to follow speed changes of the camshaft with goodresponsiveness, and the accuracy of valve timing control can be ensured.

And, because the counter-electromotive force of the motor changes incorrespondence with the motor speed, when a motor counter-electromotiveforce parameter (the counter-electromotive force or a parametercorrelated with this) is used, although the motor counter-electromotiveforce parameter may be calculated in correspondence with the actualspeed of the motor, alternatively a motor counter-electromotive forceparameter may be calculated in correspondence with a required motorspeed calculated on the basis of the speed of the camshaft and therequired speed difference. If this is done, the motorcounter-electromotive force parameter used in the calculation of themotor control value can be calculated feed-forwardly, and the sameeffects as those mentioned above can be obtained.

Now, as shown in FIG. 12, when the motor speed changes, thecounter-electromotive force of the motor changes and the effectivevoltage (the difference between the battery voltage and thecounter-electromotive force) changes. And when the motor speed isincreasing, as the motor speed increases the effective voltagedecreases, and conversely, when the motor speed is increasing, as themotor speed increases the effective voltage increases.

So, preferably, the motor control value is corrected on the basis of themotor speed and/or whether it is increasing or decreasing. If this isdone, even when the effective voltage changes with the motor speed andwhether it is increasing or decreasing, the motor control value can becorrected in correspondence with that. Therefore, it is possible tocalculate an appropriate motor control value without an influence ofvariation in the effective voltage being suffered. This correction ofthe motor control value may be applied in a system wherein a duty value(excitation rate) for duty-controlling the power supplied to the motoris calculated as the motor control value. In duty control, by the dutyvalue for a supplied voltage being regulated, the pulse width of thesupplied voltage is regulated and the power supplied to the motor isregulated. However, even at the same duty value, when the effectivevoltage (the difference between the battery voltage and thecounter-electromotive force) changes, because the amplitude of thesupplied voltage pulse changes, the power supplied to the motor changescorrespondingly. Accordingly, if the duty value is corrected on thebasis of the motor speed and whether it is increasing or decreasing, theduty value and the pulse width of the supplied voltage can be correctedfor the effective voltage changing and the amplitude of the suppliedvoltage pulse changing with the motor speed and whether it is increasingor decreasing. As a result, it is possible to compensate for changes insupplied power caused by amplitude variation of the supplied voltagepulse by correcting the supplied voltage pulse width.

And, a limit value may be set on at least one among the valve timingchange rate, the speed difference between the motor and the camshaft,and the motor speed. If this is done, because the valve timing changerate, the difference between the motor and the camshaft, and the motorspeed can be limited with a limit value, it is possible to avoid failureand damage caused by actuation exceeding guarantee limits of thevariable valve timing device.

Other features and effects of the invention will become clear from thedescription of embodiments thereof using drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic construction view of an overall control system ina first embodiment of the invention;

FIG. 2 is a schematic construction view of a variable valve timingdevice;

FIG. 3 is a flow chart showing the flow of processing of a variablevalve timing control program of the first embodiment;

FIG. 4 is a flow chart showing the flow of processing of a motor controlvalue calculation program of the first embodiment;

FIG. 5 is a graph showing conceptually a map of a required torque TAreq;

FIG. 6 is a graph showing conceptually a map of a camshaft side losstorque TB;

FIG. 7 is a graph showing conceptually a map of a loss torque TC in thevariable valve timing device;

FIG. 8 is a graph showing conceptually a map of a counter-electromotiveforce E of a motor;

FIG. 9 is a flow chart showing part of the flow of processing of a motorcontrol value calculation program of a second embodiment;

FIG. 10 is a flow chart showing part of the flow of processing of amotor control value calculation program of a third embodiment;

FIG. 11A is a graph showing conceptually a map of an effective voltagecorrection coefficient K for when a motor speed is increasing;

FIG. 11B is a graph showing conceptually a map of an effective voltagecorrection coefficient K for when a motor speed is decreasing;

FIG. 12 is a graph showing a relationship between an effective voltageand a motor speed and whether it is increasing or decreasing;

FIG. 13 is a flow chart showing the flow of processing of a motorcontrol value calculation program of a fourth embodiment;

FIG. 14 is a flow chart showing a part of the flow of processing of amotor control value calculation program of a fifth embodiment;

FIG. 15 to FIG. 17 are flow charts showing the flow of processing of anactual valve timing calculation program in a sixth embodiment;

FIG. 18 and FIG. 19 are flow charts illustrating an actual valve timingcalculation program in a seventh embodiment;

FIG. 20 is a timing chart showing an example of actual valve timingcalculation in the seventh embodiment;

FIG. 21 is a view illustrating a variation range of valve timing andrate-limited regions in an eighth embodiment of the invention;

FIG. 22 is a graph showing a relationship between engine speed andactual valve timing;

FIG. 23 is a graph showing a relationship between valve timing changerate and slowing-down variation;

FIG. 24 is a flow chart showing the flow of processing of a valve timingchange rate limit control program of the eighth embodiment;

FIG. 25 is a flow chart showing the flow of processing of a valve timingchange rate limit control program of a ninth embodiment;

FIG. 26 is a flow chart showing the flow of processing of a target valvetiming calculation program of the ninth embodiment;

FIG. 27 is a flow chart showing the flow of processing of a valve timingchange rate limit control program of a tenth embodiment;

FIG. 28 is a flow chart showing the flow of processing of a referenceposition learning prioritizing control program of an eleventhembodiment;

FIG. 29 is a flow chart showing the flow of processing of a referenceposition learning abnormality determination program of a twelfthembodiment;

FIG. 30 is a flow chart showing the flow of processing of a valve timingchange rate limit control program of the twelfth embodiment;

FIG. 31 is a flow chart showing the flow of processing of a referenceposition learning prioritizing control program of a thirteenthembodiment;

FIG. 32 is a flow chart showing the flow of processing of a pre-startingreference position learning control program of a fourteenth embodiment;

FIG. 33 is a flow chart showing the flow of processing of a pre-startingreference position learning control program of a fifteenth embodiment;

FIG. 34 is a flow chart showing the flow of processing of a pre-startingreference position learning control program of a sixteenth embodiment;

FIG. 35 is a flow chart showing the flow of processing of a main valvetiming control program of a seventeenth embodiment;

FIG. 36 is a flow chart showing the flow of processing of an engineforward rotation/backward rotation determination program of theseventeenth embodiment;

FIG. 37 is a flow chart showing the flow of processing of a valve timingcontrol program for forward engine rotation in the seventeenthembodiment;

FIG. 38 is a flow chart showing the flow of processing of a valve timingcontrol program for a stopped engine in the seventeenth embodiment;

FIG. 39 is a flow chart showing the flow of processing of a valve timingcontrol program for backward engine rotation in the seventeenthembodiment;

FIG. 40 is a flow chart showing the flow of processing of a referenceposition arrival determination program of the seventeenth embodiment;

FIG. 41 is a time chart showing an example of variable valve timingcontrol in the seventeenth embodiment;

FIG. 42 is a flow chart showing the flow of processing of an engineforward rotation/backward rotation determination program of aneighteenth embodiment;

FIG. 43 is a flow chart showing the flow of processing of an enginerotation state determination program of a nineteenth embodiment;

FIG. 44 is a flow chart showing the flow of processing of a valve timingcontrol program for a stopped engine in a twentieth embodiment;

FIG. 45 is a flow chart showing the flow of processing of a valve timingcontrol program for a stopped engine in a twenty-first embodiment;

FIG. 46 is a flow chart showing a flow of processing of a valve timingcontrol program of a stopped engine in a twenty-second embodiment;

FIG. 47 is a flow chart showing a flow of processing of a referenceposition arrival determination program of a twenty-third embodiment;

FIG. 48 is a flow chart showing a flow of processing of a referenceposition arrival determination program of a twenty-fourth embodiment;

FIG. 49 is a flow chart showing a flow of processing of a referenceposition arrival determination program of a twenty-fifth embodiment; and

FIG. 50 is a flow chart showing a flow of processing of a variable valvetiming device operating condition alteration program of a twenty-sixthembodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

(First Embodiment)

A first embodiment of the invention applied to a variable valve timingcontrol device for intake valves will now be described, on the basis ofFIG. 1 through FIG. 8. First, the outline construction of the overallsystem will be described, on the basis of FIG. 1. Power from thecrankshaft 12 of an internal combustion engine 11 is transmitted by atiming chain 13 (or a timing belt) via sprockets 14, 15 to anintake-side camshaft 16 and an exhaust-side camshaft 17. A motor-drivenvariable valve timing device 18 is provided on the intake-side camshaft16 side. This variable valve timing device 18 varies the rotation phase(camshaft phase) of the intake-side camshaft 16 with respect to thecrankshaft 12 and thereby varies the valve timing of intake valves (notshown) driven to open and close by the intake-side camshaft 16.

A cam angle sensor 19 for outputting a cam angle signal at intervals ofa predetermined cam angle is mounted beside the intake-side camshaft 16.And a crank angle sensor 2 of or outputting a crank angle signal atintervals of a predetermined crank angle is mounted beside thecrankshaft 12.

Next, on the basis of FIG. 2 the outline construction of the variablevalve timing device 18 will be described. A phase varying mechanism 21of the variable valve timing device 18 is made up of an outer gear 22 (afirst rotating member), with internal teeth, disposed concentricallywith the intake-side camshaft 16; an inner gear 23 (a second rotatingmember), with external teeth, disposed inside and concentrically withthis outer gear 22; and a planetary gear 24 (a phase-varying member),disposed between and meshing with the outer gear 22 and the inner gear23. The outer gear 22 is provided so as to rotate integrally with thesprocket 14, which rotates synchronously with the crankshaft 12. Theinner gear 23 is provided so as to rotate integrally with theintake-side camshaft 16. The planetary gear 24, by turning so as todescribe a circular orbit about the inner gear 23 while meshing with theouter gear 22 and the inner gear 23, performs the role of transmittingthe rotary power of the outer gear 22 to the inner gear 23, and also, bythe turning speed (revolving speed) of the planetary gear 24 withrespect to the rotational speed of the inner gear 23 being changed,adjusts the rotation phase (camshaft phase) of the inner gear 23 withrespect to the outer gear 22.

A motor 26 for varying the turning speed of the planetary gear 24 isprovided on the engine 11. The output shaft 27 of this motor 26 isdisposed coaxially with the intake-side camshaft 16, the outer gear 22and the inner gear 23, and the output shaft 27 of this motor 26 and asupport shaft 25 supporting the planetary gear 24 are connected by aconnecting member 28 extending in the radial direction. As a result,along with rotation of the motor 26 the planetary gear 24 can turn(revolve) along its circular orbit around the inner gear 23 whilerotating (autorotating) about the support shaft 25. A motor speed sensor29 (see FIG. 1) for detecting the rotational speed RM (the speed of theoutput shaft 27) of the motor 26 is mounted on the motor 26.

In this variable valve timing device 18, when the speed RM of the motor26 is matched to the speed RC of the intake-side camshaft 16, so thatthe revolving speed of the planetary gear 24 is matched to therotational speed of the inner gear 23 (and the rotational speed of theouter gear 22), the rotation phase difference between the outer gear 22and the inner gear 23 is held steady and the valve timing (camshaftphase) is thereby held steady.

When the valve timing of the intake valves is to be advanced, the speedRM of the motor 26 is made faster than the speed RC of the intake-sidecamshaft 16, so that the revolving speed of the planetary gear 24 ismade faster than the rotational speed of the inner gear 23. By thismeans, the rotation phase of the inner gear 23 with respect to the outergear 22 is advanced, and the valve timing (camshaft phase) is advanced.

When on the other hand the valve timing of the intake valves is to beretarded, the speed RM of the motor 26 is made slower than the speed RCof the intake-side camshaft 16, so that the revolving speed of theplanetary gear 24 is made slower than the rotational speed of the innergear 23. By this means, the rotation phase of the inner gear 23 withrespect to the outer gear 22 is retarded and the valve timing is therebyretarded.

The outputs of the various sensors mentioned above are inputted to anengine control unit (hereinafter, “ECU”) 30. This ECU 30 is constructedaround a microcomputer, and by executing various engine control programsstored in ROM thereof (a storage medium) controls the fuel injectionquantities of fuel injection valves (not shown) and the ignition timingof spark plugs (not shown) in accordance with the running state of theengine.

The ECU 30 also executes a variable valve timing control program shownin FIG. 3 and a motor control value calculation program shown in FIG. 4,which will be further discussed later. By executing these programs,first, it calculates a required valve timing change rate Vreq so as tominimize a deviation D between a target valve timing VTtg and an actualvalve timing VT of the intake valves. On the basis of this requiredvalve timing change rate Vreq it calculates a required speed differenceDMCreq between the motor 26 and the camshaft 16. And it calculates amotor control value (for example a motor applied voltage value) so as tocontrol a speed difference DMC between the motor 26 and the camshaft 16to the required speed difference DMCreq. By this means it controls therotation of the motor 26 so as to control the speed difference DMCbetween the motor 26 and the camshaft 16 to the required speeddifference DMCreq, and thereby controls the actual valve timing VT ofthe intake valves to the target valve timing VTtg. The detailedprocessing content of these programs will be explained below.

The variable valve timing control program shown in FIG. 3 is executedfor example at intervals of a predetermined period after an ignitionswitch (not shown) is turned on. When this program starts, first, in astep 101, a target valve timing VTtg is calculated on the basis of therunning state of the engine. Processing then proceeds to step 102, andcalculates an actual valve timing VT on the basis of the crank anglesignal outputted from the crank angle sensor 20 and the cam angle signaloutputted from the cam angle sensor 19. The calculation of the actualvalve timing VT can also be carried out as set forth in a sixthembodiment which will be described later.

After the calculation of the actual valve timing VT, processing proceedsto step 103 and calculates the deviation D between the target valvetiming VTtg and the actual valve timing VT. Then, in step 104, incorrespondence with this deviation D, a required valve timing changerate Vreq is calculated so as to minimize the deviation D, using a mapor the like. This required valve timing change rate Vreq for exampleassumes a plus value when the direction of the change in valve timing isto the advanced angle side and a minus value when it is to the retardedangle side. The processing of this step 104 performs the role ofrequired valve timing change rate calculating means referred to in theScope of Patent Claim.

After that, processing proceeds to step 105 and determines whether ornot a limit rate Vs has been set with respect to the valve timing changerate. This limit rate Vs is a relatively slow valve timing change rate,at which tooth grinding and damage of the gear mechanism (the gears 22to 24) do not occur for example even if a moving part for limiting therange of movement of the phase varying mechanism 21 strikes a stopperpart. A limit rate Vs is set at times such as: [1] when the actual valvetiming VT is within a rate-limited region set near a most retarded angleposition or near a most advanced angle position; [2] when valve timingreference position learning has not been completed; and [3] when it hasbeen determined that there is an abnormality of reference positionlearning (erroneous reference position learning). Setting of the limitrate Vs with respect to the valve timing change rate will be explainedin detail in a seventh embodiment to be described later.

When in this step 105 it is determined that a limit rate Vs has beenset, processing proceeds to step 106 and determines whether or not theabsolute value of the required valve timing change rate Vreq is largerthan the limit rate Vs. If as the result of this it is determined thatthe absolute value of the required valve timing change rate Vreq islarger than the limit rate Vs, processing proceeds to step 107 andguard-processes the absolute value of the required valve timing changerate Vreq with the limit rate Vs. After that, processing proceeds tostep 108.

When on the other hand in step 105 it is determined that a limit rate Vshas not been set, or when in step 106 it has been determined that theabsolute value of the required valve timing change rate Vreq is notlarger than the limit rate Vs, processing proceeds to step 108 withoutchanging the required valve timing change rate Vreq calculated incorrespondence with the deviation D between the target valve timing VTtgand the actual valve timing VT.

In this step 108, using the required valve timing change rate Vreq [°CA/s], a required speed difference DMCreq [rpm] between the motor 26 andthe camshaft 16 is calculated by means of Exp. (1).DMCreq=Vreq×60×G/720° CA  (1)

Here, G is the reduction ratio of the phase varying mechanism 21, and isthe ratio of the relative amount of turn of the motor 26 with respect tothe camshaft 16 to the valve timing variation (camshaft phasevariation). The processing of this step 108 performs the role ofrequired speed difference calculating means referred to in the Scope ofPatent Claim.

After the calculation of the required speed difference DMCreq,processing proceeds to step 109 and executes the motor control valuecalculating program shown in FIG. 4 and calculates a motor controlvalue. This motor control value calculation program shown in FIG. 4performs the role of motor control value calculating means referred toin the Scope of Patent Claim.

When this program is started, first, in a step 201, it is determinedwhether or not the deviation D between the target valve timing VTtg andthe actual valve timing VT is below a predetermined value. If thedeviation D is below the predetermined value, processing proceeds tostep 202 and sets a required motor speed RMreq to the camshaft speed RC,as shown by Exp. (2).RMreq=RC  (2)

If on the other hand in step 201 it is determined that the deviation Dis larger than the predetermined value, processing proceeds to step 203and sets the required motor speed RMreq to a value obtained by addingthe required speed difference DMCreq to the camshaft speed RC, as shownby Exp. (3).RMreq=RC+DMCreq  (3)

After the required motor speed RMreq is set in step 202 or step 203 asdescribed above, processing proceeds to step 204. In step 204, using themap of required torque TAreq shown in FIG. 5 or a numerical formula, arequired torque TAreq corresponding to the difference between therequired motor speed RMreq and the camshaft speed RC is calculated. Thisrequired torque TAreq is the net torque needed to revolve the planetarygear 24 at the required motor speed RMreq (a torque not including anyloss torque inside the variable valve timing device 18 or loss torque onthe camshaft 16 side). The map of required torque TAreq shown in FIG. 5is set on the basis of the change characteristic of the required torqueTAreq with respect to the difference between the required motor speedRMreq and the camshaft speed RC.

After that, processing proceeds to step 205 and calculates a loss torqueTB of the camshaft 16 side corresponding to the camshaft speed RC, usingthe map of camshaft 16 side loss torque TB shown in FIG. 6 or anumerical formula. This camshaft 16 side loss torque TB is the torqueconsumed as a result of drive losses on the camshaft 16 side. The map ofcamshaft 16 side loss torque TB shown in FIG. 6 is set on the basis ofthe change characteristic of the camshaft 16 side loss torque TB withrespect to the camshaft speed RC.

In the following step 206, using the map of loss torque TC in thevariable valve timing device 18 shown in FIG. 7 or a numerical formula,a loss torque TC in the variable valve timing device 18 corresponding tothe speed difference DMC between the motor 26 and the camshaft 16 (thedifference between the motor speed RM and the camshaft speed RC) iscalculated. This loss torque TC in the variable valve timing device 18is a torque consumed as a result of frictional losses in the variablevalve timing device 18. The map of loss torque TC in the variable valvetiming device 18 shown in FIG. 7 is set on the basis of the changecharacteristic of the loss torque TC in the variable valve timing device18 with respect to the speed difference DMC between the motor 26 and thecamshaft 16.

After that, processing proceeds to step 207, and adds the loss torque TBon the camshaft 16 side and the loss torque TC in the variable valvetiming device 18 to the required torque TAreq to obtain a required motortorque TMreq needed to control the motor speed RM to the required motorspeed RMreq, as shown in Exp. (4).TMreq=TAreq+TB+TC  (4)

After that, processing proceeds to step 208, and by means of a map orthe like converts the required motor torque TMreq into a required motorvoltage VD. After that, processing proceeds to step 209, and calculatesa counter-electromotive force E of the motor 26 corresponding to themotor speed RM, making use of the map of counter-electromotive force Eof the motor 26 shown in FIG. 8 or a numerical formula. The map of thecounter-electromotive force E of the motor 26 shown in FIG. 8 is set onthe basis of the change characteristic of the counter-electromotiveforce E of the motor 26 with respect to the motor speed RM.

Then, in the following step 210, the counter-electromotive force E isadded to the required motor voltage VD to obtain a motor applied voltageVM needed to control the motor speed RM to the required motor speedRMreq, as shown in Exp. (5).VM=VD+E  (5)

By the above processing, when the deviation D between the target valvetiming VTtg and the actual valve timing VT is larger than apredetermined value, the required motor speed RMreq is set to the valueobtained by adding the required speed difference DMCreq to the camshaftspeed RC, and a motor applied voltage VM needed to control the motorspeed RM to the required motor speed RMreq (=camshaft speed RC+requiredspeed difference DMCreq) is calculated. By this means, the speed of themotor 26 is feed-forward-controlled so that the speed difference DMCbetween the motor 26 and the camshaft 16 is made to match the requiredspeed difference DMCreq, and the actual valve timing VT can be made tochange in the direction of the target valve timing VTtg with goodresponsiveness.

And when the deviation D between the target valve timing VTtg and theactual valve timing VT falls to below the predetermined value, therequired motor speed RMreq is set to the camshaft speed RC and the motorapplied voltage VM needed to control the motor speed RM to the requiredmotor speed RMreq (=camshaft speed RC) is calculated. By this means, therotation of the motor 26 is controlled so as to bring the speeddifference DMC between the motor 26 and the camshaft 16 to 0, and theactual valve timing VT is stably held at or near the target valve timingVTtg. In this way it is possible to control an actual valve timing to atarget valve timing by motor drive with good accuracy, and valve timingcontrol accuracy can be improved.

And, the variable valve timing device 18 of this first embodiment isconstructed with the outer gear 22, disposed concentrically with thecamshaft 16 and rotationally driven by the rotary driving power of thecrankshaft 12; the inner gear 23, which rotates integrally with thecamshaft 16; the planetary gear 24, which transmits the rotary power ofthe outer gear 22 to the inner gear 23 and changes the relative rotationphase between the gears 22, 23; and the motor 26, which turns thisplanetary gear 24 along a circular orbit concentric with the camshaft16. Consequently, it is not necessary for the motor 26 as a whole to berotated, and the inertial weight of the rotating system of the variablevalve timing device 18 can be lightened and the motor 26 can beconnected directly to outside electrical wiring by fixed connectionmeans, and overall it is possible to raise the durability of thevariable valve timing device 18. Furthermore, the construction of thevariable valve timing device 18 is relatively simple, and therequirements of cost minimization can be satisfied.

Now, the output of the motor 26 is also consumed as frictional losses inthe variable valve timing device 18 and drive losses on the camshaft 16side. Because of this, the motor control value (for example, motorapplied voltage) needed to control the speed difference DMC between themotor 26 and the camshaft 16 to the required speed difference DMCreqvaries with the drive losses in the variable valve timing device 18 andon the camshaft 16 side. And, because a counter-electromotive forcearises in the motor 26 when the motor 26 rotates, the motor controlvalue needed to control the speed difference DMC between the motor 26and the camshaft 16 to the required speed difference DMCreq also varieswith the counter-electromotive force of the motor 26.

In view of these circumstances, in this first embodiment, the motorcontrol value is calculated using a loss torque TC consumed byfrictional losses in the variable valve timing device 18, a loss torqueTB consumed by drive losses in on the camshaft 16 side, and thecounter-electromotive force E of the motor 26. And because changes indrive losses in the variable valve timing device 18 and on the camshaft16 side and changes in the counter-electromotive force of the motor 26are taken into account in the calculation of the motor control valuelike this, the motor control value needed to control the speeddifference DMC between the motor 26 and the camshaft 16 to the requiredspeed difference DMCreq can be calculated with good accuracy withoutinfluences of frictional losses and counter-electromotive force and soon being suffered.

And, in the first embodiment, because the required valve timing changerate Vreq is limited with a limit rate Vs, failure and damage of thevariable valve timing device 18 caused by sudden operation can beprevented.

(Second Embodiment)

The motor control value calculating program shown in FIG. 9 executed ina second embodiment of the invention is one obtained by changing theprocessing of step 206 and step 209 of FIG. 4 described in the firstembodiment to processing of a step 206 a and a step 209 a respectively,and the processing of the other steps is the same as in FIG. 4.

In the first embodiment described above, in step 206 of FIG. 4, the losstorque TC in the variable valve timing device 18 was calculated incorrespondence with the speed difference DMC between the motor 26 andthe camshaft 16 (the difference between the motor speed RM and thecamshaft speed RC), and in step 209 the counter-electromotive force E ofthe motor 26 was calculated in correspondence with the motor speed RM.However, in this second embodiment, in step 206 a of FIG. 9, the losstorque TC in the variable valve timing device 18 is calculated incorrespondence with the required speed difference DMCreq between themotor 26 and the camshaft 16 (the difference between the required motorspeed RMreq and the camshaft speed RC), and in step 209 a thecounter-electromotive force E of the motor 26 is calculated incorrespondence with the required motor speed RMreq.

In this case, because the loss torque TC in the variable valve timingdevice 18 and the counter-electromotive force E of the motor 26 used forthe calculation of the motor control value can be calculatedfeed-forwardly, the responsiveness of the motor rotation control can beimproved. By this means, even under operating conditions in which theengine speed (the camshaft speed RC) changes suddenly, such as onracing, it is possible to make the motor speed RM follow changes in thecamshaft speed RC with good responsiveness, and valve timing controlaccuracy can be ensured.

(Third Embodiment)

Next, a third embodiment of the invention will be described, using FIG.10 through FIG. 12. As shown in FIG. 12, when the motor speed RMchanges, the counter-electromotive force of the motor 26 changes and theeffective voltage (the difference between the battery voltage and thecounter-electromotive force) changes. And the effective voltage differswhen the motor speed RM is increasing from when it is decreasing.

In this third embodiment, by the motor control value calculating programshown in FIG. 10 being executed, a duty value for performing dutycontrol of the power supply to the motor 26 is calculated as the motorcontrol value. In this duty control, by the duty value (excitation rate)of a supply voltage being regulated, the pulse width of the supplyvoltage is regulated and the supply of power to the motor 26 isregulated. In this case, even when the duty value is the same, when theeffective voltage (the difference between the battery voltage and thecounter-electromotive force) changes, the amplitude of the supplyvoltage pulse changes, and consequently the power supply to the motor 26changes correspondingly.

So, in this third embodiment, by the motor control value calculatingprogram shown in FIG. 10 being executed, the duty value is corrected onthe basis of the motor speed RM and whether it is increasing ordecreasing. By this means it is possible to correct the duty value toallow for the effective voltage changing with the motor speed RM andwhether it is increasing or decreasing.

The motor control value calculating program shown in FIG. 10 is oneobtained by changing the processing of steps 208 to 210 of FIG. 4explained in the foregoing first embodiment to the processing of steps208 b to 210 b, and the processing of the other steps is the same as inFIG. 4.

In this program, in step 207, a required motor torque TMreq needed tocontrol the motor speed RM to the required motor speed RMreq iscalculated. After that, processing proceeds to step 208b and convertsthe required motor torque TMreq into a required duty value DDuty using amap or the like.

After that, processing proceeds to step 209 b, and using the maps ofeffective voltage correction coefficient K for when the motor speed isincreasing and when the motor speed is decreasing shown in FIG. 11(a)and (b) or a numerical formula, an effective voltage correctioncoefficient K corresponding to the motor speed RM and whether it isincreasing or decreasing is calculated.

As shown in FIG. 12, when the motor speed is increasing, the faster isthe motor speed RM the smaller is the effective voltage (the differencebetween the battery voltage and the counter-electromotive force), andwhen the motor speed is decreasing, the slower is the motor speed RM thesmaller is the effective voltage. Because of this, the map of effectivevoltage correction coefficient K for when the motor speed is increasingshown in FIG. 11(a) is set so that the effective voltage correctioncoefficient K is made larger and a final duty value Duty is made largerthe faster is the motor speed RM. And the map of effective voltagecorrection coefficient K for when the motor speed is decreasing shown inFIG. 11(b) is set so that the effective voltage correction coefficient Kis made larger and the final duty value Duty is made larger the sloweris the motor speed RM.

After the calculation of the effective voltage correction coefficient K,processing proceeds to step 210 b and corrects the required duty valueDDuty with the effective voltage correction coefficient K as shown byExp. (6) to obtain a final duty value Duty needed to control the motorspeed RM to the required motor speed RMreq.Duty=DDuty×K  (6)

In the third embodiment described above, the duty value was corrected incorrespondence with the motor speed RM and whether it is increasing ordecreasing. Consequently, the duty value can be corrected and the pulsewidth of the supply voltage corrected to allow for the effective voltagechanging and the amplitude of the supply voltage pulse changing with themotor speed RM and whether it is increasing or decreasing. As a result,changes in the supplied power caused by amplitude changes of the supplyvoltage pulse can be compensated for by correction of the pulse width ofthe supply voltage. By this means it is possible to perform stable motorrotation control that does not suffer any influence of the effectivevoltage changing with the motor speed RM and whether it is increasing ordecreasing.

(Fourth Embodiment)

In the foregoing first embodiment, the required speed difference DMCreqwas added to the camshaft speed RC to obtain the required motor speedRMreq, and a motor control value was calculated so as to control themotor speed RM to the required motor speed RMreq. With respect to this,in a fourth embodiment of the invention shown in FIG. 13, basic controlvalues for controlling the motor speed RM to a basic motor speed RMbasethe same as the camshaft speed RC are calculated, change control valuesfor changing the motor speed RM by the required speed difference DMCreqwith respect to the basic motor speed RMbase are calculated, and a motorcontrol value is calculated on the basis of the basic control values andthe change control values.

In the motor control value calculating program shown in FIG. 13 executedin this fourth embodiment, first, in a step 301, it is determinedwhether or not the deviation D between the target valve timing VTtg andthe actual valve timing VT is equal to or below a predetermined value.If this deviation D is equal to or below the predetermined value,processing proceeds to step 302 and resets a required torque TAreq, aloss torque differential ΔTB, a loss torque TC and acounter-electromotive force differential ΔE, which will be furtherdiscussed later, all to “0” before proceeding to step 307.

When on the other hand in step 301 it is determined that the deviation Dbetween the target valve timing VTtg and the actual valve timing VT islarger than the predetermined value, processing proceeds to step 303. Instep 303, using the map of required torque TAreq shown in FIG. 5 or anumerical formula, a required torque TAreq corresponding to the requiredspeed difference DMCreq (the difference between the required motor speedRMreq and the camshaft speed RC) is calculated. After that, processingproceeds to step 304, and if it is a time of transition (a time when thecamshaft speed RC is changing), a loss torque differential ΔTB of thecamshaft 16 side corresponding to a camshaft speed differential ΔRC iscalculated using the map of the loss torque TB of the camshaft 16 sideshown in FIG. 6 or a numerical formula.

After that, processing proceeds to step 305 and, using the map of losstorque TC in the variable valve timing device 18 shown in FIG. 7 or anumerical formula, calculates a loss torque TC in the variable valvetiming device 18 corresponding to the speed difference DMC between themotor 26 and the camshaft 16 (the difference DMC between the motor speedRM and the camshaft speed RC). Next, in step 306, using the map ofcounter-electromotive force E of the motor 26 shown in FIG. 8 or anumerical formula, a counter-electromotive force differential ΔE of themotor 26 corresponding to a motor speed differential ΔRM (motor speed RM−basic motor speed RMbase) is calculated.

The required torque TAreq, the loss torque differential ΔTB of thecamshaft 16 side, the loss torque TC in the variable valve timing device18, and the counter-electromotive force differential ΔE of the motor 26constitute change control values for changing the motor speed RM by therequired speed difference DMCreq with respect to the basic motor speedRMbase (=camshaft speed RC).

After that, processing proceeds to step 307 and, using the map of losstorque TB of the camshaft 16 side shown in FIG. 6 or a numericalformula, calculates a loss torque TB of the camshaft 16 sidecorresponding to the camshaft speed RC. In step 308, using the map ofcounter-electromotive force E of the motor 26 shown in FIG. 8 or anumerical formula, a basic counter-electromotive force Ebase of themotor 26 corresponding to the basic motor speed RMbase (=camshaft speedRC) is calculated. The loss torque TB of the camshaft 16 side and thebasic counter-electromotive force Ebase of the motor 26 constitute basiccontrol values for controlling the motor speed RM to the basic motorspeed RMbase (=camshaft speed RC).

In the following step 309, as shown in Exp. (7), the loss torque TB andloss torque differential ΔTB of the camshaft 16 side and the loss torqueTC in the variable valve timing device 18 are added to the requiredtorque TAreq to obtain a required motor torque TMreq needed to controlthe motor speed RM to the required motor speed RMreq.TMreq=TAreq+TB+ΔTB+TC  (7)

After that, processing proceeds to step 310 and, using a map or the liketo convert the required motor torque TMreq into a required motor voltageVD. In step 311, as shown in Exp. (8), the basic counter-electromotiveforce Ebase and the counter-electromotive force differential ΔE areadded to the required motor voltage VD to obtain a motor applied voltageVM needed to control the motor speed RM to the required motor speedRMreq.VM=VD+Ebase+ΔE  (8)

By the above processing, when the deviation D between the target valvetiming VTtg and the actual valve timing VT has become larger than apredetermined value, a motor applied voltage VM is calculated on thebasis of basic control values (TAreq, ΔTB, TC, ΔE) for controlling themotor speed RM to the basic motor speed RMbase (=camshaft speed RC) andchange control values (TB, Ebase) for changing the motor speed RM by therequired speed difference DMCreq with respect to the basic motor speedRMbase. By this means it is possible to feed-forwardly control the speedof the motor 26 so as to make the speed difference DMC between the motor26 and the camshaft 16 match the required speed difference DMCreq andthereby change the actual valve timing VT in the direction of the targetvalve timing VTtg with good responsiveness.

And when the deviation D between the target valve timing VTtg and theactual valve timing VT has fallen below the predetermined value, a motorapplied voltage VM needed for controlling the motor speed RM to thebasic motor speed RMbase (=camshaft speed RC) is calculated. By thismeans, the speed of the motor 26 is controlled so as to bring the speeddifference DMC between the motor 26 and the camshaft 16 to 0 and theactual valve timing VT is stably held at or near the target valve timingVTtg. In this way also it is possible to control an actual valve timingto a target valve timing by motor drive with good accuracy, and valvetiming control accuracy can be improved.

(Fifth Embodiment)

A motor control value calculating program shown in FIG. 14 executed in afifth embodiment of the invention is one obtained by changing theprocessing of step 305 and step 306 of FIG. 13 explained in theforegoing fourth embodiment to processing of a step 305 a and a step 306a respectively, and the processing of the other steps is the same as inFIG. 13.

In the foregoing fourth embodiment, in step 305 of FIG. 13 a loss torqueTC in the variable valve timing device 18 was calculated incorrespondence with the speed difference DMC between the motor 26 andthe camshaft 16 (the difference between the motor speed RM and thecamshaft speed RC), and in the following step 306 acounter-electromotive force differential ΔE of the motor 26 wascalculated in correspondence with a motor speed differential ΔRM (motorspeed RM−basic motor speed RMbase). With respect to this, in this fifthembodiment, in step 305 a of FIG. 14, a loss torque TC in the variablevalve timing device 18 is calculated in correspondence with the requiredspeed difference DMCreq between the motor 26 and the camshaft 16 (thedifference between the required motor speed RMreq and the camshaft speedRC). And in the following step 306 a a counter-electromotive forcedifferential ΔE of the motor 26 is calculated in correspondence with arequired motor speed differential ΔRMreq (required motor speedRMreq−basic motor speed RMbase).

In this way it is possible to calculate the loss torque TC in thevariable valve timing device 18 and the counter-electromotive forcedifferential ΔE of the motor 26 used in the calculation of the motorcontrol value feed-forwardly. Accordingly, the responsiveness of themotor rotation control can be improved and the same effects as those ofthe foregoing second embodiment can be obtained.

Now, although in the fourth and fifth embodiments a motor appliedvoltage was calculated as the motor control value, alternatively a dutyvalue may be calculated as the motor control value. And in this case, asin the third embodiment, the duty value may be corrected on the basis ofthe motor speed and whether it is increasing or decreasing.

And although in the first to fifth embodiments a limit value (limit rateVs) was placed on the valve timing change rate, alternatively a limitvalue may be placed on the speed difference between the motor 26 and thecamshaft 16 or on the motor speed. Furthermore, these limit values maybe made to change in correspondence with the running state of the engine(for example the engine speed, cooling water temperature, intakeairflow, load etc.).

Also, on the basis of the state of convergence with respect to thetarget values of the valve timing and the valve timing change rate, themotor control value or the control parameters used in the calculation ofthe motor control value (the required torque TAreq, the loss torque TBof the camshaft 16 side, the loss torque TC in the variable valve timingdevice 18, the counter-electromotive force E of the motor 26, theeffective voltage correction coefficient K, etc.) may be amended, andthe results of those amendments may be learnt. And on the basis of suchamendment results the maps and/or numerical formulas used in thecalculation of the control parameters may be amended.

(Sixth Embodiment)

Next, a sixth embodiment of the invention will be described.

Many of the variable valve timing devices currently in use vary thevalve timing of intake valves or exhaust valves driven to open and closeby a camshaft by varying the rotation phase of the camshaft with respectto the crankshaft (hereinafter, “the camshaft phase”) of the internalcombustion engine. At this time, as the method for detecting the actualvalve timing (the actual camshaft phase), for example, as disclosed inJP-A-2001-355462, there is one that calculates the actual valve timingon the basis of a crank angle signal outputted from a crank angle sensorat intervals of a predetermined crank angle and a cam angle signaloutputted from a cam angle sensor at intervals of a predetermined camangle.

However, with this valve timing calculation method of related art, overthe interval from one cam angle signal being outputted to the next camangle signal being outputted (i.e. the interval over which a cam anglesignal is not outputted), it is not possible to calculate the actualvalve timing. Consequently, there has been the shortcoming that althoughin reality the actual valve timing changes continuously, it is onlypossible to update the calculated value of the actual valve timing insteps, and the precision of variable valve timing control has been lowby a corresponding amount.

In view of this, it is an object of this sixth embodiment to provide avariable valve timing device of an internal combustion engine with whichthe actual valve timing can be calculated even during the intervals whenthe cam angle signal is not being outputted, so that variable valvetiming control precision can be increased.

First, a variable valve timing control device of an internal combustionengine according to this sixth embodiment will be described in outline.A variable valve timing device according to this sixth embodiment has afirst rotating member disposed concentrically with a camshaft androtationally driven by rotary drive power from a crankshaft; a secondrotating member that rotates integrally with the camshaft; aphase-varying member that transmits rotary power from the first rotatingmember to the second rotating member and varies the rotation phase ofthe second rotating member with respect to the first rotating member;and a motor disposed concentrically with the camshaft so as to controlthe rotation phase of this phase-varying member, and is constructed sothat when the valve timing is not to be changed the speed of the motoris matched to the speed of the camshaft to match the turning speed ofthe phase-varying member to the speed of the camshaft and thereby holdthe difference in rotation phase between the first rotating member andthe second rotating member steady and thus hold the camshaft phasesteady, and when the valve timing is to be changed the speed of themotor is changed with respect to the speed of the camshaft to change theturning speed of the phase-varying member with respect to the speed ofthe camshaft and thereby vary the difference in rotation phase betweenthe first rotating member and the second rotating member and thus varythe camshaft phase. In this construction, because it is not necessaryfor the motor as a whole to be rotated, the inertial weight of therotating system of the variable valve timing device can be lightened andthe motor can be connected directly to outside electrical wiring byfixed connection means, and overall it is possible to raise thedurability of the variable valve timing device. Furthermore, theconstruction of the variable valve timing device is relatively simple,and the requirements of cost minimization can also be satisfied.

And, in a variable valve timing device which varies valve timing byvarying the speed of a motor with respect to the speed of the camshaft,as in the sixth embodiment, the valve timing variation (camshaft phasevariation) varies in correspondence with the difference between thespeed of the motor and the speed of the camshaft. Because of this, it ispossible to calculate the valve timing variation on the basis of thedifference between the speed of the motor and the speed of the camshaft.

Focusing on this point, in the sixth embodiment, every time the camangle signal is outputted from the cam angle sensor, the actual valvetiming at the time of outputting of the cam angle signal is calculatedon the basis of that cam angle signal and a crank angle signal outputtedfrom the crank angle sensor; with a predetermined computation period avalve timing variation is calculated on the basis of the differencebetween the motor speed and the camshaft speed; and with thepredetermined computation period a final actual valve timing iscalculated on the basis of the actual valve timing at the time ofoutputting of the cam angle signal and the valve timing variation.

Specifically, a final actual valve timing can be obtained by calculatinga valve timing variation per computation period and accumulating thiscalculated value, resetting the accumulated value of the valve timingvariation every time the cam angle signal is outputted, and adding tothe calculated value of the actual valve timing at the most recentoutputting of the cam angle signal the accumulated value of the valvetiming variation subsequent to that.

Because a valve timing variation calculated on the basis of thedifference between the motor speed and the camshaft speed can becalculated even in the intervals when the cam angle signal is not beingoutputted, if in the intervals when the cam angle signal is not beingoutputted the valve timing variation since the most recent outputting ofthe cam angle signal is calculated, a final actual valve timing can beobtained precisely by adding to the actual valve timing at the time ofthe most recent outputting of the cam angle signal the valve timingvariation subsequent to that. By this means it is possible to calculatethe actual valve timing continuously with good precision even in theintervals when the cam angle signal is not being outputted, and theprecision of variable valve timing control can be increased.

Now, although it is conceivable to calculate the camshaft speed to beused in calculating the valve timing variation on the basis of theoutput period of the cam angle signal, because generally the number ofoutputtings of the cam angle signal per revolution of the camshaft issmall, it is difficult to detect fluctuations of the camshaft speed,which fluctuates with the combustion stroke of each cylinder, from theoutput period of the cam angle signal. On the other hand, because thenumber of crank angle signals outputted from the crank angle sensor ismuch greater than the number of cam angle signals, if the crank anglesignal is used it is possible to detect fluctuation of the crankshaftspeed, which fluctuates with the combustion stroke of each cylinder.

Accordingly, in view of the relationship that the camshaft rotates onceper two revolutions of the crankshaft, the value of ½ of the crankshaftspeed detected on the basis of the output period of the crank anglesignal of the crank angle sensor can be used as the camshaft speed data.If this is done, the valve timing variation can be calculated using amore accurate camshaft speed than when the camshaft speed is detectedfrom a smaller number of cam angle signals, and the actual valve timingcalculation precision can be improved.

When the internal combustion engine is stopped, because the camshaftspeed is 0, a final actual valve timing can be obtained by adding to thecalculated value of the actual valve timing of when the engine stops anaccumulated value of subsequent valve timing variation, or a finalactual valve timing can be obtained with an accumulated value of valvetiming variation from a reference position. By this means, even when theinternal combustion engine is stopped, the actual valve timing can becalculated with good precision, and even when the internal combustionengine is stopped the actual valve timing can be controlled to a targetvalue. And, even when the actual valve timing of when the engine stopsis unclear, an actual valve timing can be calculated with an accumulatedvalue of valve timing variation from a mechanical reference position(for example a most retarded angle position) or a reference positiondetected by other means.

And, considering that when the cam angle sensor fails the cam anglesignal ceases to be outputted, when the cam angle sensor has failed afinal actual valve timing can be obtained by adding to the calculatedvalue of the actual valve timing at the time of the last outputting ofthe cam angle signal before the failure an accumulated value of valvetiming variation subsequent to that, or a final actual valve timing canbe obtained with an accumulated value of valve timing variation from areference position. By this means, even when the cam angle sensor fails,the actual valve timing can be calculated with good precision, and evenwhen the cam angle sensor has failed the actual valve timing can becontrolled to a target value. And, when the actual valve timing ofbefore the cam angle sensor failed is unclear, an actual valve timingcan be calculated with an accumulated value of valve timing variationfrom a mechanical reference position (for example a most retarded angleposition) or a reference position detected by other means.

A variable valve timing control device according to the sixth embodimentwill now be described in detail on the basis of the figures. The systemconstruction of a variable valve timing control device according to thesixth embodiment is the same as that shown in FIG. 1 and FIG. 2 and sowill not be described again here.

The ECU 30 in the sixth embodiment, by executing a variable valve timingcontrol program (not shown), feedback-controls the variable valve timingdevice 18 so as to make the actual valve timing of intake valves match atarget valve timing.

At this time, by executing an actual valve timing calculation programshown in FIG. 15 through FIG. 17, the ECU 30 calculates an actual valvetiming VTC at a time of sensor output on the basis of a crank anglesignal outputted from the crank angle sensor 20 and a cam angle signaloutputted from the cam angle sensor 19. Also, it calculates a valvetiming variation ΔVT on the basis of the difference between the motorspeed RM of the motor 26 and the camshaft speed RC of the intake-sidecamshaft 16. And it obtains a final actual valve timing VT by adding tothe actual valve timing VTC at the time of outputting of the cam anglesignal the subsequent valve timing variation ΔVT.

The actual valve timing calculation program shown in FIG. 15 throughFIG. 17 is executed at intervals of a predetermined period after anignition switch (not shown) is turned on. When this program is started,first, in a step 401, it is determined whether or not the engine isrunning, for example on the basis of whether or not an engine speedcalculated from the output period of the crank angle signal outputtedfrom the crank angle sensor 20 is 0.

If it is determined that the engine is running, processing proceeds tostep 402 and determines whether or not the cam angle sensor 19 isnormal, on the basis of a failure diagnosis result of a cam angle sensorfailure diagnosis program (not shown). When the result of this is thatthe cam angle sensor 19 is determined to be normal (not failed),processing proceeds to step 403 and determines whether or not a camangle signal outputted from the cam angle sensor 19 has been inputted.

When it is determined that a cam angle signal has been inputted,processing proceeds to step 404 and stores the input time Tcam of thecam angle signal in memory (not shown) of the ECU 30. After that,processing proceeds to step 405 and stores in memory the input time Tcrkof the crank angle signal outputted from the crank angle sensor 20immediately thereafter.

After this, processing proceeds to step 406 and calculates a timedifference TVT of the cam angle signal relative to the crank anglesignal using Exp. (9).TVT=Tcrk−Tcam+K  (9)

Here, K is a correction amount for correcting a difference of responselag between the cam angle sensor 19 and the crank angle sensor 20.

Then, in the following step 407, using the time difference TVT of thecam angle signal relative to the crank angle signal, a rotation phaseVTB of the cam angle signal relative to the crank angle signal iscalculated in accordance with Exp. (10).VTB=TVT/T 120×120° CA  (10)

Here, T120 is the time needed for the crankshaft 12 to rotate through120° CA, and is calculated on the basis of the output signal of thecrank angle sensor 20.

After this, processing proceeds to step 408 and determines whether ornot the valve timing has been controlled to a reference position (forexample a most retarded angel position). If the valve timing is at thereference position, processing proceeds to step 409 and learns thepresent rotation phase of the cam angle signal relative to the crankangle signal (the camshaft phase) VTB as a reference position (referencecamshaft phase) VTBK of the rotation phase of the intake-side camshaft16 with respect to crankshaft 12, as shown in Exp. (11), beforeproceeding to step 410.VTBK=VTB  (11)

On the other hand, when in step 408 it is determined that the valvetiming is not at the reference position, processing proceeds to step 410without carrying out the reference position learning processing of step409. In step 410, as shown in Exp. (12), using the present rotationphase VTB of the cam angle signal relative to the crank angle signal andthe reference position VTBK, the rotation phase VTC of the cam anglesignal based on the reference position VTBK is calculated. This becomesan actual valve timing VTC at the time of outputting of the cam anglesignal.VTC=VTB−VTBK  (12)

The processing of these steps 403 to 410 performs the role of cam anglesignal output time valve timing calculating means referred to in theScope of Patent Claim, and calculates an actual valve timing VTC at thetime of outputting of a cam angle signal on the basis of the cam anglesignal and the crank angle signal every time the cam angle signal isinputted (outputted).

After this, processing proceeds to step 411, and resets valve timingvariations ΔVTH, ΔVTS, which will be further discussed later, both to“0” every time the actual valve timing VTC at the time of outputting ofa cam angle signal is calculated. After that, processing proceeds tostep 419 and calculates a final actual valve timing VT using Exp. (13).VT=VTC+ΔVTH+ΔVTS  (13)

Thus, at the time of inputting (time of outputting) of a cam anglesignal, because ΔVTH=0 and ΔVTS=0 as a result of the reset processing ofstep 411, VT=VTC.

When on the other hand in step 403 it is determined that a cam anglesignal has not been inputted, processing proceeds to step 412 of FIG. 16and calculates the speed difference DMC [rpm] between the motor speed RM[rpm] of the motor 26 and the camshaft speed RC [rpm] of the intake-sidecamshaft 16, as shown by Exp. (14).DMC=RM−RC  (14)

In this case, as the camshaft speed RC of the intake-side camshaft 16,as shown in Exp. (15), the value of ½× the speed of the crankshaft 12(the engine speed) calculated on the basis of the output period of thecrank angle signal outputted from the crank angle sensor 20 is used.camshaft speed RC=crankshaft speed×½  (15)

After this, processing proceeds to step 413 and converts the speeddifference DMC [rpm] into a per-second rotation difference [rev/s] inaccordance with Exp. (16).RVT=DMC/60  (16)

Then, in the following step 414, a valve timing variation dVTH percomputation period P[s] of the valve timing variation ΔVTH (theexecution period of this program) is calculated using Exp. (17).dVTH=RVT/G×720° CA×P  (17)

Here, G is the reduction ratio of the phase varying mechanism 21, and isthe ratio of the relative amount of turn of the motor 26 with respect tothe intake-side camshaft 16 to the valve timing variation (camshaftphase variation).

After this, processing proceeds to step 415 and calculates the valvetiming variation ΔVTH by accumulating the valve timing variation dVTHper computation period P as shown by Exp. (18).ΔVTH=ΔVTH+dVTH  (18)

The processing of these steps 412 to 415 performs the role of valvetiming variation calculating means referred to in the Scope of PatentClaim, and obtains a valve timing variation ΔVTH subsequent to the mostrecent outputting of a cam angle signal by accumulating the valve timingvariation dVTH per computation period over the interval over which a camangle signal is not inputted.

And the processing of these steps 412 to 415 is executed even when instep 402 of FIG. 15 it is determined that the cam angle sensor 19 hasfailed. That is, when the cam angle sensor 19 has failed, the valvetiming variation dVTH per computation period P is accumulated to obtainthe valve timing variation ΔVTH from the last outputting of a cam anglesignal before the cam angle sensor 19 failed to the present.

After the calculation of the valve timing variation ΔVTH, processingproceeds to step 419 of FIG. 15 and calculates a final actual valvetiming VT using the above Exp. (13). When the cam angle sensor 19 hasfailed, because ΔVTS=0, VT=VTC+ΔVTH.

When on the other hand in step 401 it is determined that the engine isstopped, processing proceeds to step 416 of FIG. 17. In step 416, theper-second rotation difference RVT [rev/s] is calculated using only themotor speed RM [rpm] of the motor 26, as shown in Exp. (19).RVT=RM/60  (19)

After this, processing proceeds to step 417 and calculates a valvetiming variation dVTS per computation period P[s] of the valve timingvariation ΔVTS (i.e. the execution period of this program) in accordancewith Exp. (20).dVTS=RVT/G×720° CA×P  (20)

Here, G is the reduction ratio of the phase varying mechanism 21.

After this, processing proceeds to step 418 and accumulates the valvetiming variation dVTS per computation period P to obtain the valvetiming variation ΔVTS from the last outputting of a cam angle signalbefore the stoppage to the present.ΔVTS=ΔVTS+dVTS  (21)

The processing of these steps 416 to 418 also performs the role of valvetiming variation calculating means referred to in the Scope of PatentClaim.

After the calculation of the valve timing variation ΔVTS, processingproceeds to step 419 of FIG. 15 and calculates a final actual valvetiming VT using the above Exp. (13). Here, because while the engine isstopped ΔVTH=0, VT=VTC+ΔVTS. The processing of this step 419 performsthe role of final valve timing calculating means referred to in theScope of Patent Claim.

By the processing described above, every time a cam angle signal isinputted while the engine is running, the actual valve timing VTC at thetime of outputting of the cam angle signal is calculated on the basis ofthe cam angle signal and the crank angle signal. And when a cam anglesignal is inputted (outputted), because the valve timing variationsΔVTH, ΔVTS are reset to 0 by the reset processing of step 411, theactual valve timing VTC at the time of outputting of a cam angle signalitself becomes the final actual valve timing VT.

On the other hand, in the intervals when a cam angle signal is notinputted, on the basis of the speed difference DMC between the motor 26and the intake-side camshaft 16, a valve timing variation dVTH percomputation period is calculated and accumulated. And a final actualvalve timing VT is obtained by adding to the actual valve timing VTC atthe time of the most recent outputting of a cam angle signal the valvetiming variation ΔVTH (the accumulated value of dVTH) subsequent tothat. By this means it becomes possible to calculate the actual valvetiming VT continuously with good precision even in the intervals when acam angle signal is not inputted, and the precision of variable valvetiming control can be increased.

And when the engine is stopped, a final actual valve timing VT isobtained by adding to the actual valve timing VTC at the last time ofoutputting of a cam angle signal before the stoppage the valve timingvariation ΔVTS subsequent to that. Consequently, even when the engine isstopped, the actual valve timing VT can be calculated with goodprecision and the actual valve timing VT can be controlled to a targetvalue.

And when the cam angle sensor 19 has failed, a final actual valve timingVT is obtained by adding to the actual valve timing VTC at the last timeof outputting of a cam angle signal before the failure the valve timingvariation ΔVTH subsequent to that. Consequently, even when the cam anglesensor 19 has failed, the actual valve timing VT can be calculated withgood precision and the actual valve timing VT can be controlled to atarget value.

Alternatively, at times of engine stoppage or failure of the cam anglesensor 19, the actual valve timing may be calculated with an accumulatedvalue of valve timing variation from a mechanical reference position(for example a most retarded angle position) or from a referenceposition detected by other means.

(Seventh Embodiment)

Next, a seventh embodiment will be described. In the sixth embodimentdescribed above, a valve timing variation ΔVT was calculated on thebasis of the motor speed RM of the motor 26 and the camshaft speed RC ofthe intake-side camshaft 16, and a final actual valve timing VT wasobtained by adding to the actual valve timing VTC at the time ofoutputting of a cam angle signal the valve timing variation ΔVTsubsequent to that.

With respect to this, in a seventh embodiment, the difference betweenthe motor speed RM of the motor 26 and the camshaft speed RC of theintake-side camshaft 16 (the valve timing variation ΔVT) is calculatedon the basis of a variation in the rotation angle of the motor 26 and avariation in the rotation angle of the camshaft, and a final valvetiming is obtained by adding to the actual valve timing VTC at the timeof outputting of a cam angle signal the valve timing variation ΔVTsubsequent to that.

The seventh embodiment, in which the valve timing variation ΔVT iscalculated on the basis of a variation in the rotation angle of themotor 26 and a variation in the rotation angle of the camshaft, will nowbe described using the flow chart of FIG. 18 and FIG. 19. FIG. 18 showsprocessing carried out instead of the processing for calculating thevalve timing variation ΔVTH during engine running of FIG. 16 explainedin the sixth embodiment. And FIG. 19 shows processing carried outinstead of the processing for calculating the valve timing variationΔVTS during engine stoppage of FIG. 17. The processing shown in the flowchart of FIG. 15 in the sixth embodiment is executed in exactly the sameway in the seventh embodiment.

First, the flow chart of FIG. 18 will be described. FIG. 18 isprocessing for calculating the actual valve timing after a cam anglesignal is inputted while the engine is running. In this processing, avariation in motor rotation angle and a variation in camshaft rotationangle are compared. To compare a variation in motor rotation angle witha variation in camshaft rotation angle, in the seventh embodiment, acomparison is made between a count value of a motor angle signal outputcounter and a count value of a crankshaft angle signal output counter.

Here, the reason for using the crank angle signal instead of using thecamshaft signal is that the crankshaft and the camshaft are connected ata reduction ratio of ½, and in addition to it being possible to deduce acamshaft angle signal by using the crank angle signal, generally thenumber of crankshaft pulses is greater than the number of camshaftpulses. Because of this it is possible to obtain a variation in thecamshaft rotation angle more precisely by using the crank angle signalthan by using the cam angle signal.

In this embodiment, there are 36 crankshaft pulses at intervals of 10°CA, and the pulses actually used in computation are pulses at intervalsof 30° CA. That is, 12 pulses are used. For the motor 26, on the otherhand, pulses at intervals of 30° CA are used.

However, there is a reduction of ½ between the camshaft and thecrankshaft. So, first, in a step 420, for example the count value of thecrank angle signal is corrected to ½ to make the angle of change per onecount of the count value of the angle of the motor 26 and the countvalue of the crank angle signal the same. Conversely, the count value ofthe angle of the motor 26 may be corrected by being doubled. In this waythe angle variations of one count value of both counters are made thesame, and processing proceeds to step 421.

In step 421, a variation of the crank angle is calculated. In practice,a variation is calculated on the basis of the count value of the crankangle signal counted from the time of the previous computation to thetime of the present computation (variation of crank angle counter=crankangle counter at this time computation−crank angle counter at last timecomputation).

Then, processing proceeds to step 422 and calculates a variation in theangle of the motor 26. In practice, a variation is calculated on thebasis of the count value of the angle signal of the motor 26 countedfrom the time of the previous computation to the time of the presentcomputation (variation of motor angle counter=motor angle counter atthis time computation−motor angle counter at last time computation).

Then, in the following step 423, the difference between the variation ofthe crank angle counter and the variation of the motor angle counter iscalculated, and in step 424 a motor angle variation with respect to thecamshaft is calculated. Specifically, in step 424, a motor anglevariation with respect to the camshaft is computed using the equationshown by “motor angle variation with respect to camshaft=(variation ofmotor angle counter−variation of crank angle counter)×angle per 1count”.

Next, in step 425, the motor angle variation with respect to thecamshaft is corrected by the reduction ratio 1/G of the valve timingalteration part, and a valve timing variation dVTH per computationperiod is calculated (valve timing variation dVTH =motor angle variationwith respect to camshaft/G (reduction ratio)). Here, G is the reductionratio of the phase-varying mechanism 21 of the variable valve timingdevice 18, and is the ratio of the relative amount of turn of the motor26 with respect to the intake-side camshaft 16 to the valve timingvariation (camshaft phase variation).

After this, processing proceeds to step 426 and calculates a final valvetiming variation ΔVTH by accumulating the phase of the valve timingchanged from the last computation to the present computation, that is,the valve timing variation dVTH, with the valve timing variation ΔVTH upto the previous time, as shown in Exp. (22).ΔVTH=ΔVTH(i−1)+dVTH  (22)

The processing of these steps 420 to 426 performs the role of valvetiming variation calculating means referred to in the Scope of PatentClaim, and calculates a valve timing variation ΔVTH of an interval overwhich a cam angle signal is not inputted.

And, even when in step 402 of FIG. 15 it is determined that the camangle sensor 19 has failed, it is possible to execute the processing ofFIG. 18 and accumulate a valve timing variation dVTH of while the camangle sensor 19 is failed and thereby obtain a valve timing variationΔVTH of from the last outputting of a cam angle signal before the camangle sensor 19 failed to the present. By this means it is possible tocompute the actual valve timing precisely even when the cam angle sensor19 has failed.

After the calculation of the valve timing variation ΔVTH, processingproceeds to step 419 of FIG. 15 and calculates a final actual valvetiming VT using the above Exp. (13). When the cam angle sensor 19 hasfailed, because ΔVTS=0, VT=VTC+ΔVTH.

An example of calculating the actual valve timing by the processing ofthe flow chart of FIG. 18 described above is shown in the timing chartof FIG. 20. In the processing shown in the flow chart of FIG. 18, on thebasis of a difference between a variation of the angle of the motor 26and a variation of the angle of the camshaft, a final actual valvetiming VT is obtained by adding to an actual valve timing VTC at thetime of outputting of a cam angle signal a valve timing variation ΔVTHsubsequent to that. Therefore, as shown in the timing chart of FIG. 20,it is possible to calculate an actual valve timing VT continuously withgood precision even in the intervals when a cam angle signal is notinputted, and variable valve timing control precision can be increased.

On the other hand, when in step 401 of the flow chart of FIG. 15 it wasdetermined that the engine is stopped, the processing of FIG. 19 isexecuted. The processing of this FIG. 19 is for calculating a valvetiming variation ΔVTS of when the engine is stopped.

First, in a step 427, a variation of the angle of the motor 26 iscalculated. In practice, the variation is calculated on the basis of thecount value of the angle signal of the motor 26 counted from the time ofthe previous computation to the time of the present computation(variation of motor angle counter=motor angle counter at this timecomputation−motor angle counter at last time computation). Then, in step428, an angle variation of the motor 26 with respect to the camshaft iscalculated with only the variation of the motor angle of the motor 26.Specifically, it is calculated using the equation “motor angle variationwith respect to camshaft=variation of motor angle counter×angle per 1count”.

Next, in step 429, the angle variation of the motor 26 with respect tothe camshaft is corrected by the reduction ratio 1/G of the valve timingalteration part, and a valve timing variation dVTS is calculated (valvetiming variation dVTS=motor angle variation with respect to camshaft/G(reduction ratio)).

After this, processing proceeds to step 430, and calculates a finalvalve timing variation ΔVTS by accumulating the valve timing changedfrom the last computation time to the present computation time, that is,the valve timing variation dVTS, with the valve timing variation ΔVTS upto the previous time, as shown in Exp. (23).ΔVTS=ΔVTS(i−1)+dVTS  (23)

Thus, the processing shown in the flow chart of FIG. 19 performs therole of valve timing variation calculating means referred to in theScope of Patent Claim.

After the valve timing variation ΔVTS is calculated, processing proceedsto step 419 of FIG. 15 and calculates a final actual valve timing VT(VT=VTC+ΔVTH+ΔVTS). Here, because the engine is stopped, VTH=0, andVT=VTC+ΔVTS. The processing of the above step 419 performs the role offinal valve timing calculating means referred to in the Scope of PatentClaim.

As described above, in the processing of FIG. 18, while the engine isrunning, in the case where a valve timing variation has been calculatedfrom a comparison of a motor angle variation and a camshaft anglevariation also, in the same way as when a valve timing variation wascalculated on the basis of speed differences between the motor and theintake-side camshaft, a final actual valve timing VT is obtained byadding to an actual valve timing VTC at the time of outputting of a camangle signal, constituting a guide, a valve timing variation ΔVTHsubsequent to that. By this means it becomes possible to calculate theactual valve timing VT continuously with good precision even in theintervals when a cam angle signal is not outputted, and the precision ofvariable valve timing control can be increased.

And when the engine is stopped, a final actual valve timing VT isobtained by adding to the actual valve timing VTC at the last time ofoutputting of a cam angle signal before the stoppage the valve timingvariation ΔVTS subsequent to that. Consequently, even when the engine isstopped, the actual valve timing VT can be calculated with goodprecision and the actual valve timing VT can be controlled to a targetvalue even when the engine is stopped.

And when the cam angle sensor 19 has failed, a final actual valve timingVT is obtained by adding to the actual valve timing VTC at the last timeof outputting of a cam angle signal before the failure the valve timingvariation ΔVTH subsequent to that. Consequently, even when the cam anglesensor 19 has failed, the actual valve timing VT can be calculated withgood precision and the actual valve timing VT can be controlled to atarget value.

Alternatively, at times of engine stoppage or failure of the cam anglesensor 19, the actual valve timing may be calculated with an accumulatedvalue of valve timing variation from a mechanical reference position(for example a most retarded angle position) or from a referenceposition detected by other means.

And, the variable valve timing devices 18 of the sixth and seventhembodiments described above have an outer gear 22 (first rotatingmember) disposed concentrically with a camshaft 16 and rotationallydriven by rotary drive power from a crankshaft 12; an inner gear 23(second rotating member) that rotates integrally with the camshaft 16; aplanetary gear 24 (phase-varying member) that transmits rotary powerfrom the outer gear 22 to the inner gear 23 and varies the relativerotation phase between the gears 22, 23; and a motor 26 that turns thisplanetary gear 24 around a circular orbit concentric with the camshaft16, and is constructed so that when the valve timing is not to bechanged the speed of the motor 26 is matched to the speed of thecamshaft 16 to match the turning speed of the planetary gear 24 to thespeed of the camshaft 16 and thereby hold the difference in rotationphase between the outer gear 22 and the inner gear 23 steady and holdthe camshaft phase steady, and when the valve timing is to be changedthe speed of the motor 26 is changed with respect to the speed of thecamshaft 16 to change the turning speed of the planetary gear 24 withrespect to the speed of the camshaft 16 and thereby change thedifference in rotation phase between the outer gear 22 and the innergear 23 and change the camshaft phase. In this construction, because itis not necessary for the motor 26 as a whole to be rotated, the inertialweight of the rotating system of the variable valve timing device 18 canbe lightened and the motor 26 can be connected directly to outsideelectrical wiring by fixed connection means, and overall it is possibleto raise the durability of the variable valve timing device 18.Furthermore, the construction of the variable valve timing device 18 isrelatively simple, and the requirements of cost minimization can also besatisfied.

And, although in the foregoing first embodiment through seventhembodiment variable valve timing control devices for intake valves havebeen described, the invention is not limited to variable valve timingcontrol devices for intake valves and may alternatively be applied to avariable valve timing control device for exhaust valves. Also, thephase-varying mechanism of the variable valve timing device 18 is notlimited to one using a planetary gear mechanism as in the embodimentsdescribed above, and alternatively a phase-varying mechanism of someother type may be used, and in short it may be any motor-driven variablevalve timing device that varies a valve timing by varying the speed of amotor with respect to the speed of a camshaft.

(Eighth Embodiment)

Next, an eighth embodiment of the invention will be described.

Generally, in a variable valve timing device, a limit position of therange of variation of the valve timing (a variable valve timingvariation range limit position) is mechanically enforced by a movingpart of the phase-varying mechanism being made to abut with a stopperpart. Because of this, when the valve timing is controlled to avariation range limit position of a variable valve timing device (a mostretarded angle position or a most advanced angle position) or to theproximity thereof, it sometimes happens that it overshoots and themoving part of the phase-varying mechanism is not sufficiently slowedand strikes the stopper part. And due to the impact load at the time ofthis impact a large load acts on the meshing parts of the gears of thephase-varying mechanism, there is a risk of the gears grinding andbecoming locked and of the gear mechanism suffering damage, and there isa possibility of it becoming impossible to control the valve timingnormally.

Because of this, it is an object of the eighth embodiment to provide avariable valve timing control device with which it is possible toprevent grinding and damage of the gear mechanism of a variable valvetiming device when a valve timing is controlled to a variation rangelimit position of the variable valve timing device or to the proximitythereof, and with which it is possible to improve the reliability ofoperation of the variable valve timing device.

First, a variable valve timing control device of an internal combustionengine according to the eighth embodiment will be described in outline.A variable valve timing control device according to the eighthembodiment, when the actual valve timing is in a predeterminedrate-limited region set in the vicinity of a variation range limitposition of the variable valve timing device, executes rate-limitingcontrol for limiting the valve timing change rate to below apredetermined rate. If this is done, when the actual valve timing is inthe rate-limited region in the vicinity of the limit position, the valvetiming change rate can be slowed to below the predetermined value toforcibly slow down the speed of movement of the moving part of thephase-varying mechanism. Thus it is possible to avoid the moving part ofthe phase-varying mechanism striking the stopper part without beingslowed down, and grinding and damage of the gear mechanism can beprevented.

In this case, even when the actual valve timing is in the rate-limitedregion, when the actual valve timing is being changed in the oppositedirection from the limit position of the rate-limited region (forexample when the actual valve timing is being changed in the advancedangle direction from the vicinity of the most retarded angle position),even if the valve timing change rate is large, there will be nocollision of the moving part of the phase-varying mechanism and thestopper part. Because of this, even when the actual valve timing is inthe rate-limited region, when the actual valve timing is being changedin the opposite direction from the limit position of the rate-limitedregion, rate-limiting control need not be executed. In this way, evenwhen the actual valve timing is in the rate-limited region, when theactual valve timing is being changed in a direction such that acollision of the moving part of the phase-varying mechanism and thestopper part will not occur, the valve timing change rate can be notslowed. As a result, the actual valve timing can be changed swiftly tothe target valve timing, and responsiveness of variable valve timingcontrol can also be ensured.

Now, if the width of the rate-limited region is narrow, when the valvetiming change rate at the time of entering the rate-limited region isfast, there is a possibility of the moving part of the phase-varyingmechanism striking the stopper part without the valve timing change ratebeing slowed down sufficiently. And if the detection error (dispersion)of the actual valve timing is large, there is a possibility of themoving part of the phase-varying mechanism striking the stopper partwithout the valve timing change rate being slowed down sufficientlybecause the timing at which it is detected that the actual valve timinghas entered the rate-limited region is late. In view of thesecircumstances, it is desirable for the rate-limited region to be set onthe basis of the valve timing variation needed to slow the valve timingchange rate to below the predetermined rate and/or on the actual valvetiming detection error. If this is done, a rate-limited region can beset that has a width such that it is possible to slow down the valvetiming change rate to below a predetermined rate in view of thedetection error of the actual valve timing and the valve timingvariation needed to slow the rate. By this means it is possible to carryout stable rate-limiting control that does not suffer influences ofactual valve timing detection error and valve timing change rate. Inthis case, a valve timing change rate (or an actual valve timingdetection error) may be computed during variable valve timing controland a rate-limited region set in accordance with this computed value, orin advance, for example at the design stage, a technologist may measureor compute a maximum valve timing change rate (or a maximum actual valvetiming detection error) and set a fixed rate-limited region incorrespondence with this value and store it in memory.

A variable valve timing control device of an internal combustion engineaccording to the eighth embodiment will now be described in detail onthe basis of the drawings. The system construction of a variable valvetiming control device according to the eighth embodiment is basicallythe same as that shown in FIG. 1 and FIG. 2.

However, in the variable valve timing device 18 shown in FIG. 1 and FIG.2, to limit the variation range of the valve timing (the movable rangeof the phase varying mechanism 21), a moving part and a stopper part(both not shown) are provided on the phase varying mechanism 21. And, asshown in FIG. 21, the movable range of the phase varying mechanism 21 islimited to the range of from a position at which the moving partcontacts a retarded angle side stopper part to a position at which itcontacts an advanced angle side stopper part, to limit the variationrange of the valve timing. In this case, the position at which themoving part of the phase varying mechanism 21 contacts the retardedangle side stopper part is the most retarded angle position (retardedangle side limit position) of the phase varying mechanism 21, i.e. themost retarded angle position of the valve timing. And the position atwhich the moving part of the phase-varying mechanism 21 contacts theadvanced angle side stopper part is a most advanced angle position(advanced angle side limit position) of the phase-varying mechanism 21,i.e. the most advanced angle position of the valve timing.

The variable valve timing device 18 that is the control object of avariable valve timing control device according to the eighth embodimentis not limited to one of the construction shown in FIG. 1 and FIG. 2.That is, a variable valve timing control device according to the eighthembodiment can be applied to any variable valve timing device having agear mechanism, irrespective of the type of its drive source andphase-varying mechanism.

The ECU 30 executes the same variable valve timing control program as inthe first embodiment, shown in FIG. 3. Accordingly, it calculates arequired valve timing change rate Vreq so as to minimize the deviation Dbetween a target valve timing VTtg and the actual valve timing VT ofintake valves and controls the motor speed RM of the motor 26 so as torealize this required valve timing change rate Vreq. In this way, itmatches the actual valve timing VT of the intake valves to the targetvalve timing VTtg.

Also, the ECU 30 executes a valve timing change rate limit controlprogram shown in FIG. 24, which will be further discussed later. By thismeans it executes rate-limiting control by setting a limit rate Vs forlimiting the required valve timing change rate Vreq when the actualvalve timing VT of the intake valves is in a retarded angle siderate-limited region set in the vicinity of the most retarded angleposition or an advanced angle side rate-limited region set in thevicinity of the most advanced angle position.

As shown in FIG. 21, the retarded angle side rate-limited region is setto a range of a predetermined width α [° CA] from the most retardedangle position in the advanced angle direction, and the advanced angleside rate-limited region is set to a range of a predetermined width α [°CA] from the most advanced angle position in the retarded angledirection. The width α [° CA] of these rate-limited regions is set to avalue obtained by totalling a detection error C [° CA] of the actualvalve timing VT and a valve timing variation D [° CA] needed for slowingthe valve timing change rate V down to the limit rate Vs.α=C+D  (24)

Because, as shown in FIG. 22, the higher the engine speed NE becomes thelarger the actual valve timing VT detection error C becomes, in thisembodiment, as the actual valve timing VT detection error C, the maximumdetection error value Cmax thereof (the detection error Cmax of theactual valve timing VT at a maximum engine speed NEmax) is used.

And because, as shown in FIG. 23, the faster the valve timing changerate V becomes the larger the valve timing variation D needed forslowing it down to the limit rate Vs becomes, in this embodiment, as thevalve timing variation D needed for the slowing down, a maximum valueDmax thereof (the valve timing variation Dmax needed to slow the valvetiming change rate V down to the limit rate Vs from a maximum rate Vmax)is used.

The processing content of the valve timing change rate limit controlprogram shown in FIG. 24 executed by the ECU 30 will now be described indetail. The valve timing change rate limit control program shown in FIG.24 is executed with a predetermined period for example after an ignitionswitch is turned on.

When this program is started, first, in a step 501, it is determinedwhether or not the actual valve timing VT is in the retarded angle siderate-limited region (whether or not |most retarded angleposition−VT|≦retarded angle side rate-limited region width α). When itis determined that the actual valve timing VT is in the retarded angleside rate-limited region, processing proceeds to step 502. In step 502,it is determined whether or not the target valve timing VTtg is on theretarded angle side of the actual valve timing VT (whether or notVTtg−VT<0).

When the result is that it is determined that the target valve timingVTtg is on the retarded angle side of the actual valve timing VT,because the actual valve timing VT is in the retarded angle siderate-limited region and is changing in the direction of the mostretarded angle position, which is the limit position of that region, itis determined that there is a possibility of the moving part of thephase-varying mechanism 21 hitting the retarded angle side stopper part,and processing proceeds to step 505. In step 505, to prevent grindingand damage of the gear mechanism (the gears 22 to 24), a limit rate Vslimiting the required valve timing change rate Vreq is set andrate-limiting control is executed.

Conversely, when in the above-mentioned step 502 it is determined thatthe target valve timing VTtg is on the advanced angle side of the actualvalve timing VT (VTtg−VT>0), because the actual valve timing VT is inthe retarded angle side rate-limited region but changing in the oppositedirection from the most retarded angle position (in the advanced angledirection), it is determined that there is no possibility of the movingpart of the phase-varying mechanism 21 hitting the retarded angle sidestopper part, and processing proceeds to step 506. In step 506, thelimit rate Vs on the required valve timing change rate Vreq is canceled.

When on the other hand in the above-mentioned step 501 it is determinedthat the actual valve timing VT is not in the retarded angle siderate-limited region, processing proceeds to step 503. In step 503, it isdetermined whether or not the actual valve timing VT is in the advancedangle side rate-limited region (whether or not most advanced angleposition−VT≦advanced angle side rate-limited region width α). If it isdetermined that the actual valve timing VT is in the advanced angle siderate-limited region, processing proceeds to step 504 and determineswhether or not the target valve timing VTtg is on the advanced angleside of the actual valve timing VT (whether or not VTtg−VT<0).

When the result is that it is determined that the target valve timingVTtg is on the advanced angle side of the actual valve timing VT,because the actual valve timing VT is in the advanced angle siderate-limited region and changing in the direction of the most advancedangle position, which is the limit position of that region, it isdetermined that there is a possibility of the moving part of thephase-varying mechanism 21 hitting the advanced angle side stopper part,and processing proceeds to step 505. In step 505, to prevent grindingand damage of the gear mechanism (the gears 22 to 24), a limit rate Vslimiting the required valve timing change rate Vreq is set andrate-limiting control is executed.

Conversely, when in the above-mentioned step 504 it is determined thatthe target valve timing VTtg is on the retarded angle side of the actualvalve timing VT, then because the actual valve timing VT is in theadvanced angle side rate-limited region but changing in the oppositedirection from the most advanced angle position (in the retarded angledirection), it is determined that there is no possibility of the movingpart of the phase-varying mechanism 21 hitting the advanced angle sidestopper part, and processing proceeds to step 506. In step 506, thelimit rate Vs on the required valve timing change rate Vreq is canceled.

By the above processing, when the actual valve timing VT is in theretarded angle side or advanced angle side rate-limited region andchanging in the direction of the limit position thereof, a limit rate Vsis set and rate-limiting control is executed to limit the required valvetiming change rate Vreq to below the limit rate Vs. By this means, inthe retarded angle side or advanced angle side rate-limited region thevalve timing change rate V can be slowed down to the limit rate Vs toslow the speed of movement of the moving part of the phase-varyingmechanism 21. Consequently, it is possible to avoid the moving part ofthe phase-varying mechanism 21 hitting a stopper part at high speed. Asa result, grinding and damage of the gear mechanism (the gears 22 to 24)can be prevented, and the reliability of operation of the variable valvetiming device 18 can be increased.

On the other hand, even when the actual valve timing VT is in theretarded angle side or advanced angle side rate-limited region, when itis changing in the opposite direction from the limit position of thatregion, the limit rate Vs is canceled and rate-limiting control is notexecuted. By this means, even when the actual valve timing VT is in theretarded angle side or advanced angle side rate-limited region, when theactual valve timing VT is changing in a direction such that a collisionbetween the moving part of the phase-varying mechanism 21 and a stopperpart will not occur, slowing down of the valve timing change rate can benot carried out. Consequently, the actual valve timing VT can be made tochange swiftly to the target valve timing VTtg, and responsiveness ofvariable valve timing control can also be ensured.

Now, if the width α of the retarded angle side or advanced angle siderate-limited region is narrow, when the valve timing change rate atwhich the retarded angle side or advanced angle side rate-limited regionis entered is fast, there is a possibility of the moving part of thephase-varying mechanism 21 striking the stopper part without the valvetiming change rate being slowed down sufficiently. And if the detectionerror (dispersion) of the actual valve timing VT is large, there is apossibility of the moving part of the phase-varying mechanism 21striking the stopper part without the valve timing change rate beingslowed down sufficiently because the timing at which it is detected thatthe actual valve timing VT has entered the retarded angle side oradvanced angle side rate-limited region is late.

Because of this, in this embodiment, the width α of the retarded angleside and advanced angle side rate-limited regions is set to a valueobtained by totalling a detection error C of the actual valve timing VTand a valve timing variation D needed for sufficient slowing. Thus,retarded angle side and advanced angle side rate-limited regions havingwidths such that the valve timing change rate can be slowed down tobelow a predetermined limit rate Vs without fail can be set. Therefore,it is possible to perform stable rate-limiting control that does notsuffer influences of actual valve VT timing detection error and valvetiming change rate.

In this embodiment, rate-limited regions of the same width were set onboth the most retarded angle side and the most advanced angle side ofthe valve timing variation range (the variation range of thephase-varying mechanism 21). However, alternatively, depending on therange of valve timing actually used, the width of the retarded angleside rate-limited region and the width of the advanced angle siderate-limited region can be made different, or a rate-limited region maybe set on either the retarded angle side or the advanced angle sideonly.

(Ninth Embodiment)

Next, a ninth embodiment of the invention will be described, using FIG.25 and FIG. 26.

The ECU 30, as described in the sixth embodiment, maintains thedetection accuracy of the actual valve timing VT by learning a referenceposition of the valve timing (for example a most retarded angleposition) every time predetermined learning conditions arise (forexample every time a cam angle signal is inputted, or every time theengine is started). Therefore, when reference position learning has notbeen completed, because the detection accuracy of the actual valvetiming VT has fallen (the detection error has increased), if the valvetiming is controlled to or near to a limit position of its variationrange in this state, there is a possibility of the moving part of thephase-varying mechanism 21 hitting a stopper part at high speed.

To avoid this, in this embodiment, the ECU 30, by executing a valvetiming change rate limit control program shown in FIG. 25 with apredetermined period, when reference position learning has not beencompleted, sets a limit rate Vs limiting the required valve timingchange rate Vreq and executes rate-limiting control.

Also, the ECU 30, by executing the target valve timing calculationprogram shown in FIG. 26 with a predetermined period, when executingvariable valve timing control in a state that reference positionlearning has not been completed, calculates a target valve timing VTtgin accordance with a required valve timing change rate Vreq limited tobelow a limit rate Vs by rate-limiting control. The processing contentof these programs will be explained below.

When the valve timing change rate limit control program shown in FIG. 25is started, first, in a step 601, it is determined whether or notreference position learning is incomplete. When it is determined thatreference position learning is incomplete, because the detectionaccuracy of the actual valve timing VT has fallen (the detection errorhas increased), there is a possibility of the moving part of thephase-varying mechanism 21 being allowed to hit a stopper part at highspeed. Because of this, processing proceeds to step 602 and sets a limitrate Vs limiting the required valve timing change rate Vreq and executesrate-limiting control.

After that, this program is started, and at the stage where it isdetermined in step 601 that reference position learning has beencompleted, processing proceeds to step 603 and cancels the limit rate Vson the required valve timing change rate Vreq.

And when the target valve timing calculation program shown in FIG. 26 isstarted, first, in a step 701, it is determined whether or notrate-limiting control based on non-completion of reference positionlearning is being executed. When it is determined that rate-limitingcontrol is being executed, processing proceeds to step 702, andcalculates a target valve timing VTtg in accordance with the requiredvalve timing change rate Vreq limited to below a limit rate Vs. Thetarget valve timing VTtg in this rate-limiting control execution is setto a target valve timing such that problems such as misfiring do notoccur even at a slowed valve timing change rate.

When on the other hand it is determined that rate-limiting control isnot being executed, processing proceeds to step 703 and calculates anormal target valve timing VTtg on the basis of the engine running stateand so on.

In the ninth embodiment described above, when reference positionlearning has not been completed, rate-limiting control that limits therequired valve timing change rate Vreq to below a limit rate Vs isexecuted. Consequently, when before the completion of reference positionlearning the detection accuracy of the actual valve timing VT hasfallen, even when the valve timing is controlled to or near to a limitposition of its variation range, the moving part of the phase-varyingmechanism 21 hitting a stopper part at high speed can be avoided, and itis possible to prevent grinding and damage of the gear mechanism.

Also, in the ninth embodiment, when variable valve timing control isexecuted with reference position learning not completed, a target valvetiming VTtg in accordance with a valve timing change rate limited tobelow a limit rate Vs by rate-limiting control is set. Consequently,even when variable valve timing control is carried out at a valve timingchange rate slowed by rate-limiting control, a target valve timing VTtgcan be set so that running can be continued with quality of combustionand so on of the engine 11 maintained to a certain extent.

(Tenth Embodiment)

Whereas in the foregoing ninth embodiment when reference positionlearning had not been completed rate-limiting control was executed overthe whole valve timing region, in a tenth embodiment, when referenceposition learning has not been completed, rate-limiting control isexecuted only over a region where the difference between the actualvalve timing VT and the limit position (most retarded angle position ormost advanced angle position) is within a predetermined value (apre-learning rate-limited region).

The valve timing change rate limit control program in this embodiment isshown in FIG. 27. The valve timing change rate limit control program ofFIG. 27 is obtained by adding the processing of a step 601 a between theprocessing of step 601 and step 602 of FIG. 25, and the processing ofthe other steps is the same as in FIG. 25.

In the program shown in FIG. 27, when in step 601 it is determined thatreference position learning has not been completed, processing proceedsto step 601 a and determines whether or not the actual valve timing VTis in a predetermined pre-learning rate-limited region. Thispre-learning rate-limited region is a region where, consideringdeterioration in actual valve timing VT detection accuracy (increaseddetection error) due to reference position learning being non-completed,there is a possibility of a collision between the moving part of thephase-varying mechanism 21 and the stopper part occurring, and is set toa region wider than the rate-limited region described in the foregoingseventh embodiment (see FIG. 21).

When reference position learning has not been completed and it isdetermined that the actual valve timing VT is in the pre-learningrate-limited region, it can be inferred that there is a possibility of acollision between the moving part of the phase-varying mechanism 21 andthe stopper part occurring. So, processing proceeds to step 602 and setsa limit rate Vs for limiting the required valve timing change rate Vreqand executes rate-limiting control. Even when the actual valve timing VTis within the pre-learning rate-limited region, when it is changing inthe opposite direction from the respective limit position, the limitrate Vs may be canceled and rate-limiting control may be not executed.

On the other hand, even when reference position learning has not beencompleted, when it is determined that the actual valve timing VT is notin the pre-learning rate-limited region, it can be inferred that theprobability of a collision between the moving part of the phase-varyingmechanism 21 and the stopper part occurring is low. Therefore,processing proceeds to step 603 and cancels the limit rate Vs on therequired valve timing change rate Vreq.

In the tenth embodiment described above, when reference positionlearning has not been completed, and when the actual valve timing VT isin a pre-learning rate-limited region, rate-limiting control isexecuted. Consequently, at the time of reference position learning, inthe region where a collision between the moving part of thephase-varying mechanism 21 and the stopper part will not occur, theactual valve timing VT can be changed swiftly without the valve timingchange rate being limited, and the time required for reference positionlearning can be shortened.

In the tenth embodiment also, the target valve timing calculationprogram of FIG. 26 may be executed, so that when variable valve timingcontrol is executed in a state that reference position learning has notbeen completed a target valve timing VTtg in accordance with a valvetiming change rate limited to below a limit rate Vs by rate-limitingcontrol is set.

(Eleventh Embodiment)

In an eleventh embodiment of the invention, by a reference positionlearning prioritizing control program being executed shown in FIG. 28,until reference position learning has been completed, normal variablevalve timing control is prohibited and reference position learning onlyis made executable.

The reference position learning prioritizing control program shown inFIG. 28 is executed for example at intervals of a predetermined periodafter an ignition switch is turn on. When this program is started,first, in a step 801, it is determined whether or not reference positionlearning is non-completed. When it is determined that reference positionlearning is non-completed, processing proceeds to step 802 and prohibitsnormal variable valve timing control. After that, processing proceeds tostep 803 and sets a limit rate Vs on the required valve timing changerate Vreq.

After this, processing proceeds to step 804 and executes referenceposition learning. In this reference position learning, in a state wherethe valve timing has been controlled to a reference position (forexample, when the most retarded angle position is used as a referenceposition, the state of the moving part of the phase-varying mechanism 21having abutted with a retarded angle side stopper part), an actual valvetiming VT is calculated and this is learned as the reference position.

After that, when in step 801 it is determined that reference positionlearning has been completed, processing proceeds to step 805 and permitsnormal variable valve timing control. After that, processing proceeds tostep 806 and cancels the limit rate Vs on the required valve timingchange rate Vreq.

In the eleventh embodiment described above, until reference positionlearning is completed, normal variable valve timing control isprohibited and only reference position learning is made executable.Consequently, reference position learning can be completed and detectionaccuracy of the actual valve timing VT ensured before processing shiftsto normal variable valve timing control.

(Twelfth Embodiment)

Even when reference position learning has been completed, if anabnormality has occurred in reference position learning and a referenceposition is mis-learned, the detection error of the actual valve timingVT becomes large. Consequently, when the valve timing is controlled toor near to a limit position of its variation range, there is apossibility of the moving part of the phase-varying mechanism 21striking the stopper part at high speed.

To avoid this, in a twelfth embodiment of the invention, a referenceposition learning abnormality determination program shown in FIG. 29 anda valve timing change rate limit control program shown in FIG. 30 areexecuted. By means of these programs it is possible to determine whetherthere has been an abnormality of reference position learning, and, whenit is determined that there has been an abnormality in referenceposition learning, to set a limit rate Vs on the required valve timingchange rate Vreq and execute rate-limiting control.

The reference position learning abnormality determination program shownin FIG. 29 is executed for example with a predetermined period after anignition switch is turned on, and performs the role of learningabnormality determination means referred to in the Scope of PatentClaim. When this program is started, first, in a step 901, it isdetermined whether or not the present reference position learning valueVT0 is below an upper limit side learning guard value VTGmax. In step902, it is determined whether or not the present reference positionlearning value VT0 is above a lower limit side learning guard valueVTGmin. Here, the upper limit side learning guard value VTGmax and thelower limit side learning guard value VTGmin are values set with regardto a normal range of dispersion of the reference position arising fromindividual differences between systems, change over time and so on.

If the reference position learning value VT0 is in the normal range(VTGmin≦VT0≦VTGmax) between the upper limit side learning guard valueVTGmax and the lower limit side learning guard value VTGmin, processingproceeds to step 903 and determines that there has been no abnormalityof reference position learning (it is normal).

Conversely, if the reference position learning value VT0 is larger thanthe upper limit side learning guard value VTGmax or smaller than thelower limit side learning guard value VTGmin, that is, when thereference position learning value VT0 is not contained within the rangebetween the upper and lower side learning guard values VTGmax, VTGmin,processing proceeds to step 904. In step 904, it is determined thatthere has been an abnormality of reference position learning (referenceposition mis-learning).

And when the valve timing change rate limit control program shown inFIG. 30 is started, first, in a step 1001, it is determined whether ornot reference position learning is abnormal (whether or not thereference position has been mis-learned) on the basis of the abnormalitydetermination result of the reference position learning abnormalitydetermination program of FIG. 29 described above.

When the result is that it has been determined that reference positionlearning is abnormal (the reference position has been mis-learned),because the detection accuracy of the actual valve timing VT isdecreased (the detection error is increased), it can be inferred thatthere is a possibility of the moving part of the phase-varying mechanism21 striking the stopper part at high speed. Therefore, processingproceeds to step 1002 and sets a limit rate Vs for limiting the requiredvalve timing change rate Vreq and executes rate-limiting control.

On the other hand, when in step 1001 it is determined that referenceposition learning is normal, processing proceeds to step 1003 andcancels the limit rate Vs on the required valve timing change rate Vreq.

In the foregoing twelfth embodiment, when it is determined thatreference position learning is abnormal (the reference position has beenmis-learned), rate-limiting control limiting the required valve timingchange rate Vreq to below a limit rate Vs is executed. Consequently,even when the reference position is mis-learned and the detection errorof the actual valve timing VT increases, the moving part of thephase-varying mechanism 21 hitting the stopper part at high speed can beavoided, and it is possible to prevent grinding and damage of the gearmechanism.

In the twelfth embodiment also, the target valve timing calculationprogram of FIG. 26 may be executed, so that when variable valve timingcontrol is carried out with reference position learning abnormal atarget valve timing VTtg in accordance with a valve timing change ratelimited to below a limit rate Vs by rate-limiting control is set.

(Thirteenth Embodiment)

In a thirteenth embodiment of the invention, by a reference positionlearning prioritizing control program shown in FIG. 31 being executed,normal variable valve timing control is prohibited and only referenceposition learning is executable until reference position learning isdetermined to be normal.

The reference position learning prioritizing control program shown inFIG. 31 is one obtained by changing the processing of step 801 of FIG.28 to processing of a step 801 a, and the processing of the other stepsis the same as in FIG. 28.

In this program, first, in the step 801 a, it is determined whether ornot reference position learning is abnormal (whether or not thereference position has been mis-learned) on the basis of the abnormalitydetermination result of the reference position learning abnormalitydetermination program of FIG. 29 described above.

When the result is that it has been determined that reference positionlearning is abnormal, normal variable valve timing control is prohibitedand a limit rate Vs is set on the required valve timing change rateVreq, and then reference position learning is executed (steps 802 to804). After that, when in step 801 a it is determined that referenceposition learning is normal, normal variable valve timing control ispermitted and the limit rate Vs on the required valve timing change rateVreq is canceled (steps 805, 806).

In the thirteenth embodiment described above, normal variable valvetiming control is prohibited and only reference position learning isexecuted until it is determined that reference position learning isnormal. Consequently, reference position learning can be completednormally and detection accuracy of the actual valve timing VT can beensured before processing shifts to normal variable valve timingcontrol.

(Fourteenth Embodiment)

The motor-driven variable valve timing device 18 (see FIG. 2) can alsobe controlled before the engine 11 is started (while the engine isstopped). So, in a fourteenth embodiment, by a pre-starting referenceposition learning control program shown in FIG. 32 being executed,reference position learning is executed before starting of the engine 11(before cranking).

The pre-starting reference position learning control program shown inFIG. 32 is executed with a predetermined period from immediately afterthe power supply to the ECU 30 is turned on (immediately after anignition switch is turned from an OFF position to an ACC position or anON position). When this program is started, first, in a step 1101, it isdetermined whether or not the ignition switch has been turned to the ONposition. When the ignition switch has been turned to the ON position,processing proceeds to step 1102 and determines whether or not referenceposition learning has been completed. If reference position learning hasnot yet been completed, processing proceeds to step 1103 and executesreference position learning.

Because by this processing reference position learning is executedbefore starting of the engine 11, the actual valve timing VT can bedetected accurately from when the engine 11 is started. Therefore, theactual valve timing VT can be accurately controlled to a target valvetiming VTtg suitable for cranking, and the startability of the engine 11can be improved.

(Fifteenth Embodiment)

In a fifteenth embodiment, by a pre-starting reference position learningcontrol program shown in FIG. 33 being executed, reference positionlearning is executed before the engine 11 is started, and start control(starter operation) of the engine 11 is prohibited until referenceposition learning is completed.

When the pre-starting reference position learning control program shownin FIG. 33 is started, first, in a step 1201, it is determined whetheror not an ignition switch has been turned to an ON position. When theignition switch has been turned to the ON position, processing proceedsto step 1202 and determines whether or not reference position learninghas been completed. When reference position learning has not yet beencompleted, processing proceeds to step 1203 and prohibits operation of astarter of the engine 11 (cranking). After that, processing proceeds tostep 1204 and executes reference position learning. The processing ofthe above-mentioned step 1203 performs the role of starting prohibitionmeans referred to in the Scope of Patent Claim.

After that, when in step 1202 it is determined that reference positionlearning has been completed, processing proceeds to step 1205 andpermits operation of the starter of the engine 11. After this, if theignition switch is turned to a START position, the starter operates andthe engine 11 is started.

In the fifteenth embodiment described above, because operation of thestarter is prohibited until reference position learning completes,operation of the starter can be prevented from being commenced beforethe completion of reference position learning. In other words, referenceposition learning can be completed certainly before operation of thestarter is commenced and the engine 11 is started.

(Sixteenth Embodiment)

In a sixteenth embodiment, by a pre-starting reference position learningcontrol program shown in FIG. 34 being executed, the execution ofprocessing for prohibiting start control of the engine 11 (operation ofthe starter) is limited to a predetermined time from when the ignitionswitch is turned on.

The pre-starting reference position learning control program shown inFIG. 34 is one obtained by adding the processing of a step 1201 a afterthe processing of step 1201 of FIG. 33, and the processing of the othersteps is the same as in FIG. 33.

In this program, after it is determined in step 1201 that the ignitionswitch has been turned on (operated to an ON position), processingproceeds to step 1201 a and determines whether or not a predeterminedtime has elapsed from the ignition switch being turned on. If thepredetermined time from the ignition switch being turned on has not yetelapsed, operation of the starter of the engine 11 is prohibited by theprocessing of step 1202 and step 1203. And after reference positionlearning has completed, operation of the starter of the engine 11 ispermitted (step 1205).

When on the other hand the predetermined time from the ignition switchbeing turned on elapses before reference position learning completes,processing proceeds from step 1201 a to step 1205 and permits operationof the starter of the engine 11 even before completion of referenceposition learning.

In the sixteenth embodiment described above, processing for prohibitingthe operation of the starter of the engine 11 until reference positionlearning completes is executed only within a predetermined period fromwhen the ignition switch is turned on. Consequently, even when for somereason reference position learning cannot be completed within apredetermined period from when the ignition switch is turned on,starting control of the engine 11 (starter operation) can be commencedthereafter, and problems of the engine 11 becoming unstartable can beprevented.

Although in the foregoing eighth to sixteenth embodiments the inventionwas applied to a variable valve timing control device for intake valves,there is no limitation to this, and alternatively the invention may beapplied to a variable valve timing control device for exhaust valves.Also, the construction of the variable valve timing device 18 may bechanged as necessary, and in short it may be any valve timing controldevice for varying valve timing that uses a gear mechanism. And, thedrive source of the variable valve timing device also is not limited toa motor, and as long as it uses a gear mechanism the invention can beapplied to a variable valve timing device having hydraulic pressure as adrive source.

Besides this the invention can be implemented with any of various otherchanges, and for example can be implemented by arbitrarily combining anyof the eighth to sixteenth embodiments described above.

(Seventeenth Embodiment)

A seventeenth embodiment of the invention will now be described.

A motor-driven variable valve timing device has the characteristic thatit can vary the valve timing irrespective of the running state of theengine. Therefore, variable valve timing control can be carried out evenwhen the engine is starting or stopping. However, when the engine isstarting or stopping, reverse rotation of the engine sometimes occurs.On starting or stopping of the engine, when the engine reverse-rotateswhile variable valve timing control is being executed, the followingkind of problem arises.

The calculation of the actual valve timing based on the output signalsof the crank angle sensor and the cam angle sensor is carried out on thepremise that the engine is rotating forward; that is, that thecrankshaft and the camshaft are rotating forward. Because of this, whenthe engine reverse-rotates, the actual valve timing is mis-calculated.Therefore, when the engine reverse-rotates during variable valve timingcontrol on engine starting or stopping, the variable valve timing deviceis controlled on the basis of a mis-calculated actual valve timing.

Therefore, it is an object of the seventeenth embodiment to provide avariable valve timing control device of an internal combustion enginethat previously can prevent problems relating to variable valve timingcontrol arising as a result of reverse rotation of the internalcombustion engine and can raise the controllability of the internalcombustion engine at times of starting and stopping.

First, a variable valve timing control device of an internal combustionengine according to the seventeenth embodiment will be described inoutline. A variable valve timing control device according to theseventeenth embodiment is one that, in a system wherein a variable valvetiming device for varying the valve timing of intake valves or exhaustvalves by means of a drive source provided separately from the internalcombustion engine is controlled by valve timing control means,determines the state of rotation of the internal combustion engine withrotation state determining means and performs actual valve timingcalculation and/or variable valve timing control when determining thatthe internal combustion engine is rotating forward or is stopped.

If this is done, the state of rotation of the internal combustion enginecan be monitored and it can be arranged that actual valve timingcalculation and variable valve timing control are carried out only whenthe internal combustion engine is rotating forward or stopped. When onthe other hand reverse rotation of the internal combustion engine hasoccurred, actual valve timing calculation and normal variable valvetiming control based on output signals from a cam angle sensor and acrank angle sensor can be stopped. By this means, even when reverserotation of the internal combustion engine occurs on starting orstopping of the internal combustion engine, it is possible to preventdeterioration of valve timing control accuracy resulting from reverserotation, and the control quality of variable valve timing control onstarting and stopping of the internal combustion engine can beincreased.

In this case, preferably, the state of rotation of the internalcombustion engine is determined on the basis of output signals of acrank angle sensor and/or a cam angle sensor. A crank angle sensoroutputs a crank angle signal at intervals of a predetermined crankangle, and a cam angle sensor outputs a cam angle signal at intervals ofa predetermined cam angle. Therefore, by monitoring the output signalsof the crank angle sensor or the cam angle sensor it is possible todistinguish whether the internal combustion engine is rotating orstopped.

Also, preferably, when the internal combustion engine is rotating and itis determined that the engine speed at the time when a starter is beingturned on or when the starter is turned off is above a predeterminedvalue, it is determined that the internal combustion engine is rotatingforward. When a starter is on, because the internal combustion engine isforcibly driven to rotate forward by the drive power of the starter, itcan be determined that the internal combustion engine is rotatingforward. And although if the starter is turned off when the engine speedhas not risen sufficiently there is a possibility of the internalcombustion engine reverse-rotating, when the starter is turned off afterthe engine speed has risen sufficiently, starting of the internalcombustion engine completes normally and the internal combustion enginecontinues to rotate forward even after the starter is turned off.Therefore, if an internal combustion engine is rotating and it isdetermined that the engine speed is above a predetermined value at thetime when the starter is turned off, it can be determined that theinternal combustion engine is rotating forward.

Now, when the internal combustion engine is stopped, because no signalsare outputted from the crank angle sensor and the cam angle sensor, itis not possible to carry out a calculation of actual valve timing basedon output signals of the crank angle sensor and the cam angle sensor.

So, preferably, when variable valve timing control is to be executedwhile the internal combustion engine is stopped, the amount of actuationof the variable valve timing device after the engine stops is controlledto match the actual valve timing to the target valve timing. The amountof actuation of the variable valve timing device after the engine stopsconstitutes a parameter expressing the valve timing variation subsequentto the engine stopping. Therefore, by controlling the amount ofactuation of the variable valve timing device after the engine stops, itis possible to control the valve timing variation from an actual valvetiming calculated immediately before the engine stopped. By this means,without calculating the actual valve timing directly while the engine isstopped, it is possible to match the actual valve timing of while theengine is stopped (the actual valve timing of immediately before theengine stopped+the valve timing variation) to a target valve timingindirectly, and variable valve timing control can be executedaccurately.

When variable valve timing control is to be executed while the internalcombustion engine is stopped, in the case of a motor-driven variablevalve timing device, preferably, the amount of rotation (number ofrevolutions, rotational angle, phase variation) of the motor iscontrolled as the amount of actuation of the variable valve timingdevice. By this means it is possible to execute variable valve timingcontrol while the internal combustion engine is stopped with highaccuracy.

And when it has been determined that the internal combustion engine hasreverse-rotated, preferably, the actual valve timing is controlled to areference position. In this way it is possible to reach a state ofreadiness for the next variable valve timing control swiftly.

When the reference position is set to a limit position of the variationrange of the variable valve timing device (a most advanced angleposition or a most retarded angle position), the actual valve timing maybe controlled to the reference position while the internal combustionengine is reverse-rotating or while the internal combustion engine isstopped after it has reverse-rotated. When the reference position is setto a limit position of the variation range of the variable valve timingdevice, even if the actual valve timing is not known, the position atwhich a moving part of a phase-varying mechanism of the variable valvetiming device strikes an advanced angle side or retarded angle sidestopper part becomes the reference position (most advanced angleposition or most retarded angle position). Therefore, at any time whilethe internal combustion engine is reverse-rotating or stopped, theactual valve timing can be controlled to the reference position.

In this case, preferably, it is determined on the basis of a controloutput to the variable valve timing device whether or not the actualvalve timing has reached the reference position set to a limit positionof the variation range of the variable valve timing device. That is, itcan be determined whether or not the actual valve timing has reached thereference position on the basis of whether or not a control output tothe variable valve timing device exceeds a predetermined value needed tomake the actual valve timing reach the reference position (make themoving part of the phase-varying mechanism hit the stopper part).

On the other hand, when the reference position has been set to anintermediate position in the variation range of the variable valvetiming device, preferably, the actual valve timing is controlled to thereference position while the internal combustion engine is stopped afterhaving reverse-rotated. When the reference position has been set to anintermediate position in the variation range of the variable valvetiming device, if the actual valve timing is not known, the actual valvetiming cannot be controlled to the reference position. Therefore, it isdesirable to wait for the internal combustion engine to stop afterreverse-rotating, and control the actual valve timing to the referenceposition after a state has been reached such that the actual valvetiming can be found for example from a valve timing variation from alimit position.

A specific example of a variable valve timing control device of aninternal combustion engine according to the seventeenth embodiment willnow be described in detail on the basis of the drawings. The systemconstruction of a variable valve timing control device according to theseventeenth embodiment is basically the same as that shown in FIG. 1 andFIG. 2 and so will not be described again here.

The ECU 30 in the seventeenth embodiment, by executing the valve timingcontrol programs shown in FIG. 35 through FIG. 40, functions as rotationstate determining means and valve timing control means, and controls thevariable valve timing device 18 while monitoring the state of rotationof the engine 11.

In the seventeenth embodiment, as shown in FIG. 41, when an ignitionswitch (hereinafter, “IG switch”) is turned on, a variable valve timingdevice driving relay (hereinafter, “VCTdrive relay”) is turned on, and apower supply voltage is supplied from a battery (not shown) to the ECU30 and the variable valve timing device 18 and so on. And even after theIG switch is turned off, the ON state of the VCT drive relay ismaintained until a predetermined time elapses, and the power supplyvoltage continues to be supplied to the ECU 30 and the variable valvetiming device 18 and so on. And when the predetermined time has elapsedfrom the IG switch being turned off, the VCT drive relay is turned off,and the supply of the power supply voltage to the ECU 30 and thevariable valve timing device 18 and so on is stopped. As a result, evenwhile the engine is stopped, the variable valve timing device 18 can becontrolled until the VCT drive relay is turned off.

The ECU 30 determines the state of rotation (forward rotation/reverserotation/stopped) of the engine 11 on the basis of the output signalsfrom the crank angle sensor 20 and the cam angle sensor 19 and an on/offsignal of a starter (not shown). When it has determined that the engine11 is rotating forward or stopped, it performs actual valve timingcalculation and variable valve timing control. When a reverse rotationof the engine 11 has occurred, actual valve timing calculation andvariable valve timing control are stopped.

During forward rotation of the engine 11, a target valve timing iscalculated on the basis of the running state of the engine and so on,and an actual valve timing is calculated on the basis of the outputsignals of the crank angle sensor 20 and the cam angle sensor 19. Andthe motor 26 of the variable valve timing device 18 isfeedback-controlled so as to make the actual valve timing match thetarget valve timing.

On the other hand, while the engine 11 is stopped, because no signalsare outputted from the crank angle sensor 20 and the cam angle sensor19, it is not possible to perform calculation of an actual valve timingbased on the output signals of the crank angle sensor 20 and the camangle sensor 19. So, while the engine 11 is stopped, the amount ofrotation (number of revolutions, angle of rotation, phase variation) ofthe motor 26 of the variable valve timing device 18 after the enginestops is controlled to bring the actual valve timing to the target valvetiming. That is, because the amount of rotation of the motor 26 afterthe engine stops is a parameter expressing the valve timing variationsince the engine stopped, by controlling the amount of rotation of themotor 26 after the engine stops it is possible to control the valvetiming variation from the actual valve timing calculated immediatelybefore the engine stopped. By this means it is possible to bring theactual valve timing while the engine is stopped (the actual valve timingimmediately before the engine stopped+the valve timing variation) to atarget valve timing indirectly, without directly calculating the actualvalve timing while the engine is stopped.

And, if it is determined that the engine 11 has rotated backward,differently from normal variable valve timing control, the actual valvetiming is swiftly brought to a state of readiness for the next variablevalve timing control by being controlled to a reference position. Thisreference position is set for example to a limit position (a mostadvanced angle position or a most retarded angle position) of thevariation range of the variable valve timing device 18.

The processing content of the valve timing control programs shown inFIG. 35 through FIG. 40 executed by the ECU 30 will now be described.

[Main Valve Timing Control]

The main valve timing control program shown in FIG. 35 is executed witha predetermined period from when the IG switch is turned on to when theVCT drive relay turns off. When this program is started, first, in astep 1301, an engine rotating/stopped determination is carried out onthe basis of the output signals of the crank angle sensor 20. The enginerotating/stopped determination may alternatively be carried out on thebasis of the output signals of the cam angle sensor 19.

After this, processing proceeds to step 1302 and determines whether ornot the engine is rotating on the basis of the determination result ofstep 1301. If it is determined that the engine is not rotating (that theengine is stopped) processing proceeds to step 1305 and executes a valvetiming control program for when the engine is stopped shown in FIG. 38,which will be further discussed later, and the present program ends.

On the other hand, when in step 1302 it is determined that the engine isrotating, processing proceeds to step 1303 and executes an engineforward rotation/reverse rotation determination program shown in FIG.33, which will be further discussed later, and thereby performs anengine forward rotation/reverse rotation determination on the basis ofan on/off signal from a starter (not shown). After this, processingproceeds to step 1304 and determines whether or not the engine isrotating forward on the basis of the determination result of step 1303.If it is determined that the engine is rotating forward, processingproceeds to step 1306 and executes a valve timing control program forwhen the engine is rotating forward shown in FIG. 37, which will befurther discussed later, and the present program ends. When on the otherhand in step 1304 it is determined that the engine is not rotatingforward (i.e. the engine is rotating backward), processing proceeds tostep 1307 and executes a valve timing control program for when theengine is rotating backward shown in FIG. 39, which will be furtherdiscussed later, and the present program ends.

[Engine Forward/Reverse Rotation Determination]

When in step 1303 of the main valve timing control program of FIG. 35the engine forward rotation/reverse rotation program of FIG. 36 isstarted, first, in a step 1401, it is determined whether or not thestarter has been turned on. If as the result it is determined that thestarter has been turned on, it is determined that the engine 11 is beingforcibly driven to rotate forward by the drive power of the starter, andprocessing proceeds to step 1402. In step 1402 it is determined that theengine is rotating forward, and the present program ends.

When on the other hand it is determined in step 1401 that the starterhas not been turned on (i.e. that the starter is off), processingproceeds to step 1403. In step 1403 it is determined whether or not theengine speed at the point in time at which the starter was turned offwas above a predetermined speed such that forward rotation can bemaintained. When it is determined that the engine speed when the starterturned off was above the predetermined speed, because the engine speedrose sufficiently before the starter was turned off, it can be inferredthat starting of the engine 11 completed normally and that even afterthe starter was turned off the engine 11 has continued to rotateforward. Accordingly, processing proceeds to step 1402 and determinesthat the engine is rotating forward, whereupon the present program ends.

With respect to this, when in step 1403 it is determined that the enginespeed when the starter turned off was below the predetermined speed,because the starter was turned off before the engine speed had risensufficiently, there is a possibility that the engine 11 has rotatedbackward since the starter was turned off. Therefore, processingproceeds to step 1404 and determines that the engine is rotatingbackward, whereupon the present program ends.

[Valve Timing Control while Engine Rotating Forward]

When in step 1306 of the main valve timing control program of FIG. 35the valve timing control program for when the engine is rotating forwardshown in FIG. 37 is started, first, in a step 1501, a target valvetiming is calculated on the basis of the running state of the engine andso on. After that, processing proceeds to step 1502 and calculates anactual valve timing for example from crank angle signals outputted fromthe crank angle sensor 20 and cam angle signals outputted from the camangle sensor 19.

After this, processing proceeds to step 1503 and feedback-controls themotor 26 of the variable valve timing device 18 so as to make the actualvalve timing match the target valve timing.

As this valve timing control for when the engine is rotating forward,alternatively the same control as in for example the foregoing firstembodiment may be carried out.

[Valve Timing Control while Engine Stopped]

When in step 1305 of the main valve timing control program of FIG. 35the valve timing control program for when the engine is stopped shown inFIG. 38 is started, first, in a step 1601, a target valve timing (forexample a valve timing suited to a next engine start) is calculated.After that, processing proceeds to step 1602 and calculates a targetnumber of revolutions of the motor 26 (target amount of rotation) incorrespondence with the difference between the actual valve timingcalculated immediately before the engine stopped and the target valvetiming (the target valve timing variation).

After that, processing proceeds to step 1603 and accumulates the numberof revolutions (amount of rotation) of the motor 26 since the enginestopped to obtain an actual number of revolutions (actual amount ofrotation) of the motor 26. The number of revolutions of the motor 26 forexample is given a plus value in the forward rotation direction of themotor and a minus value in the reverse rotation direction of the motor.

After this, processing proceeds to step 1604 and determines whether ornot the actual number of revolutions of the motor 26 since the enginestopped matches the target number of revolutions. When as the result itis determined that the actual number of revolutions of the motor 26since the engine stopped does not match the target number ofrevolutions, processing proceeds to step 1605 and determines whether ornot the actual number of revolutions of the motor 26 since the enginestopped is lower than the target number of revolutions. If the actualnumber of revolutions of the motor 26 is lower than the target number ofrevolutions, processing proceeds to step 1606 and controls the motor 26to rotate forward before returning to step 1603. If on the other handthe actual number of revolutions of the motor 26 is greater than thetarget number of revolutions, processing proceeds to step 1607 andcontrols the motor 26 to rotate backward before returning to step 1603.

After that, when in step 1604 it is determined that the actual number ofrevolutions of the motor 26 since the engine stopped matches the targetnumber of revolutions, processing proceeds to step 1608 and determinesthat the actual valve timing of the stopped engine (the actual valvetiming of immediately before the engine stopped+the valve timingvariation) has reached the target valve timing. After that, processingproceeds to step 1609 and stops the motor 26 and thereby holds theactual valve timing as of that time, and the present program ends.

[Valve Timing Control while Engine Rotating Backward]

When in step 1307 of the main valve timing control program of FIG. 35the valve timing control program for when the engine is rotatingbackward of FIG. 39 is started, first, in a step 1701, a referenceposition is read in as a target valve timing. As mentioned above, thisreference position is set for example to a most advanced angle positionor a most retarded angle position constituting a limit position of thevariation range of the variable valve timing device 18.

After this, in step 1702, it is determined whether or not the targetvalve timing (reference position) is a most advanced angle position or amost retarded angle position, and if it is determined that the targetvalve timing (reference position) is a most advanced angle position or amost retarded angle position the processing of step 1703 onward isexecuted and the actual valve timing is controlled to the referenceposition (most advanced angle position or most retarded angle position)while the engine is rotating backward. When the reference position hasbeen set to the most advanced angle position or the most retarded angleposition, even if the actual valve timing is not known, the position atwhich a moving part of the phase-varying mechanism 21 of the variablevalve timing device 18 hits an advanced angle side or retarded angleside stopper part becomes the reference position (most advanced angleposition or most retarded angle position). Therefore, the actual valvetiming can be controlled to the reference position in the following wayeven while the engine is rotating backward.

First, in step 1703, a reference position arrival determination programshown in FIG. 40, which will be further discussed later, is executed,and a determination of whether or not the actual valve timing hasarrived at the reference position (most advanced angle position or mostretarded angle position) is carried out on the basis of a control outputto the motor 26.

After this, processing proceeds to step 1704 and determines whether ornot the actual valve timing has arrived at the reference position (mostadvanced angle position or most retarded angle position) on the basis ofthe determination result of step 1703. When as the result it isdetermined that the actual valve timing has not reached the referenceposition (most advanced angle position or most retarded angle position),processing proceeds to step 1705 and outputs a control value of themotor 26 so that the actual valve timing moves in the direction of thereference position (most advanced angle position or most retarded angleposition).

After that, when in step 1704 it was determined that the actual valvetiming has reached the reference position (most advanced angle positionor most retarded angle position), processing proceeds to step 1706 andupdates a stored value of the actual valve timing to the referenceposition (most advanced angle position or most retarded angle position).After that, processing proceeds to step 1707 and controls the motor 26to hold the present valve timing, and the present program ends.

Alternatively, the processing of steps 1703 to 1707 may be carriedexecuted while the engine is stopped after rotating backward, and theactual valve timing thereby controlled to the reference position (mostadvanced angle position or most retarded angle position) while theengine is stopped after rotating backward.

On the other hand, when the reference position has been set to anintermediate position in the variation range of the variable valvetiming device 18, in step 1702 the determination is “No”, and thepresent program ends without the processing of steps 1703 to 1707 beingexecuted. In this case, the actual valve timing is preferably controlledto the reference position (an intermediate position) while the engine isstopped after rotating backward. When the reference position has beenset to an intermediate position in the variation range of the variablevalve timing device 18, if the actual valve timing is not known, it isnot possible to control the actual valve timing to the referenceposition (an intermediate position). Therefore, processing first waitsuntil the engine has stopped after rotating backward, and controls theactual valve timing to the reference position after a state has beenreached such that the actual valve timing can be found for example froma valve timing variation from a limit position.

[Reference Position Arrival Determination]

When in step 1703 of the valve timing control program for while theengine is rotating backward of FIG. 39 the reference position arrivaldetermination program of FIG. 40 is started, first, in a step 1801, atarget accumulated value of the control output to the motor 26 needed tomake the actual valve timing reach the reference position (most advancedangle position or most retarded angle position) (make the moving part ofthe phase-varying mechanism 21 hit the stopper part) is calculated.After that, processing proceeds to step 1802 and obtains an actualaccumulated value of the control output to the motor 26 by accumulatingthe motor control value from when the motor 26 started to be controlledto move the actual valve timing in the direction of the referenceposition (most advanced angle position or most retarded angle position).

After this, processing proceeds to step 1803 and determines whether ornot the actual accumulated value of the control output to the motor 26has risen above the target accumulated value of the control output. Whenit is determined that the actual control output accumulated value of themotor 26 has risen above the target control output accumulated value,processing proceeds to step 1804 and infers that the actual valve timinghas arrived at the reference position (most advanced angle position ormost retarded angle position), and the present program ends.

An example of the seventeenth embodiment described above will beexplained using the time chart of FIG. 41. When the engine 11 isstarted, while the engine is stationary between the IG switch beingturned on (whereupon the VCT drive relay is turned on) and the starterbeing turned on, the valve timing control for when the engine is stoppedis carried out. That is, the actual number of revolutions of the motor26 since the engine stopped is controlled to a target number ofrevolutions to match the actual valve timing of the stopped engine to atarget valve timing.

After that, while the starter is on and the engine is rotating forward,valve timing control for when the engine is rotating forward isexecuted. That is, the motor 26 of the variable valve timing device 18is feedback-controlled to make an actual valve timing calculated on thebasis of the output signals of the crank angle sensor 20 and the camangle sensor 19 match a target valve timing.

Then, after the starter is turned off, if it is determined that theengine is rotating forward, valve timing control for when the engine isrotating forward is carried out again. However, when after the starteris turned off it is determined that the engine is rotating backward,actual valve timing calculation and variable valve timing control arestopped and the actual valve timing is returned to the referenceposition (most advanced angle position or most retarded angle position).

On stopping of the engine 11, on the other hand, while the engine isrotating forward immediately after the IG switch is turned off, valvetiming control for when the engine is rotating forward is executed.After that, if it is determined that the engine has stopped, valvetiming control for when the engine is stopped is executed until the VCTdrive relay is turned off. However, when it is determined that theengine is rotating backward, actual valve timing calculation andvariable valve timing control are stopped, and the actual valve timingis returned to the reference position (most advanced angle position ormost retarded angle position).

In the seventeenth embodiment described above, the state of rotation ofthe engine 11 is monitored, and actual valve timing calculation andvariable valve timing control are carried out only when the engine isrotating forward or stopped, and when backward rotation of the enginehas occurred, actual valve timing calculation and variable valve timingcontrol are stopped. Because of this, even when reverse rotation of theengine occurs on starting or stopping of the engine, it is possible toprevent deterioration of valve timing control accuracy resulting fromreverse rotation, and the control quality of variable valve timingcontrol on starting and stopping of the engine can be increased.

However, when the engine is stopped, it is not possible to carry outcalculation of the actual valve timing based on output signals from thecrank angle sensor 20 and the cam angle sensor 19. So, in thisseventeenth embodiment, when variable valve timing control is to beexecuted while the engine is stopped, the actual number of revolutionsof the motor 26 since the engine stopped is controlled to match a targetnumber of revolutions, to make the actual valve timing of the stoppedengine (the actual valve timing of immediately before the enginestopped+the valve timing variation) match the target valve timing. Bythis means it is possible to bring the actual valve timing of thestopped engine to the target valve timing indirectly, without directlycalculating the actual valve timing while the engine is stopped, andvariable valve timing control can be executed with good accuracy.

Also, in this seventeenth embodiment, when reverse rotation of theengine has occurred, because the actual valve timing is controlled to areference position, a state of readiness for the next variable valvetiming control can be reached swiftly.

(Eighteenth Embodiment)

Next, an eighteenth embodiment of the invention will be described.

The variable valve timing device 18 in this embodiment has aconstruction such that when the motor 26 is not being driven the outputshaft 27 of the motor 26 rotates synchronously with the intake-sidecamshaft 16. The state of rotation (rotating forward/rotatingbackward/stopped) of the motor 26 can be determined for example on thebasis of the output signal of the motor speed sensor 29. Therefore, whenthe motor 26 is rotating synchronously with the intake-side camshaft 16,it is possible to determine the state of rotation of the engine 11 bydetermining the state of rotation of the motor 26.

An engine forward rotation/reverse rotation determination program shownin FIG. 42 executed in this eighteenth embodiment is obtained by addingthe processing of two steps 1403 a, 1403 b between step 1403 and step1404 of FIG. 36 explained with reference to the seventeenth embodiment,and the processing of the other steps is the same as in FIG. 36.

In this program, when it is determined in step 1403 that the enginespeed when the starter was turned off was lower than a predeterminedengine speed at which forward rotation can be maintained, processingproceeds to step 1403 a. In step 1403 a, when the variable valve timingdevice 18 is holding the actual valve timing steady, that is, when themotor 26 is rotating synchronously with the intake-side camshaft 16,forward rotation or reverse rotation of the motor 26 is determined forexample on the basis of the output signal of the motor speed sensor 29.This forward rotation or reverse rotation of the motor 26 corresponds toforward rotation or reverse rotation of the engine 11.

After this, processing proceeds to step 1403 b and determines whether ornot the state of forward rotation being determined on the basis of thestate of rotation of the motor 26 after the starter turns off hascontinued for a predetermined time (or a predetermined number ofrevolutions). When as the result it is determined that the state offorward rotation being determined on the basis of the state of rotationof the motor 26 has continued for a predetermined time (or apredetermined number of revolutions), processing proceeds to step 1402and determines that the engine is rotating forward. When on the otherhand the state of forward rotation being determined on the basis of thestate of rotation of the motor 26 does not continue for thepredetermined time (or predetermined number of revolutions), processingproceeds to step 1404 and determines that the engine is rotatingbackward.

In this way, forward rotation/reverse rotation of the engine 11 afterthe starter is turned off can be determined more accurately.

(Nineteenth Embodiment)

In a nineteenth embodiment of the invention also, the variable valvetiming device 18 has a construction such that the output shaft 27 of themotor 26 rotates synchronously with the intake-side camshaft 16 when themotor 26 is not being driven. Because of this, it is possible todetermine the state of rotation of the engine 11 by determining thestate of rotation of the motor 26 rotating synchronously with theintake-side camshaft 16.

In this nineteenth embodiment of the invention, the engine rotationstate determination program shown in FIG. 43 is executed. When thisprogram is started, first, in a step 1901, the variable valve timingdevice 18 is set to a state in which the actual valve timing is heldsteady, that is, the state wherein the motor 26 rotates synchronouslywith the intake-side camshaft 16. After that, processing proceeds tostep 1902 and determines the state of rotation of the motor 26 (rotatingforward/rotating backward/stopped) on the basis for example of theoutput signal of the motor speed sensor 29.

After this, processing proceeds to step 1903 and determines whether ornot the motor is rotating on the basis of the determination result ofstep 1902. When it is determined that the motor is not rotating (i.e.the motor is stopped), processing proceeds to step 1905 and determinesthat the engine is stopped, and the present program ends.

On the other hand, when in step 1903 it is determined that the motor isrotating, processing proceeds to step 1904 and determines whether or notthe motor is rotating forward on the basis of the determination of step1902. When it is determined that the motor is rotating forward,processing proceeds to step 1906 and determines that the engine isrotating forward, and the present program ends.

With respect to this, when in step 1904 it is determined that the motoris not rotating forward (i.e. the motor is rotating backward),processing proceeds to step 1907 and determines that the engine isrotating backward, and the present program ends.

In the nineteenth embodiment described above, after the state whereinthe motor 26 rotates synchronously with the intake-side camshaft 16 isset, the state of rotation (rotating forward/rotating backward/stopped)of the engine 11 is determined on the basis of the state of rotation ofthe motor 26 rotating synchronously with the intake-side camshaft 16,and consequently the state of rotation of the engine 11 can bedetermined with good accuracy.

(Twentieth Embodiment)

In executing variable valve timing control while the engine is stopped,in the seventeenth embodiment, as the amount of rotation of the motor 26of the variable valve timing device 18 after the engine stops, theactual number of revolutions of the motor 26 was controlled to match atarget number of revolutions to make the actual valve timing of thestopped engine match a target valve timing. With respect to this, in atwentieth embodiment, as the amount of rotation of the motor 26, a phasevariation is used. That is, an actual phase variation (actual rotationangle) of the motor 26 after the engine stops is controlled to match atarget phase variation (target rotation angle) to make the actual valvetiming of the stopped engine match a target valve timing.

The phase variation (rotation angle) of the motor 26 can be detected bycounting a pulse signal outputted from the motor speed sensor 29 everytime the motor 26 rotates through a predetermined angle.

In the twentieth embodiment, a valve timing control program for whilethe engine is stopped shown in FIG. 44 is executed. When this program isstarted, first, in a step 2001, a target valve timing is calculated.Then, instep 2002, a target phase variation of the motor 26corresponding to the difference (a target valve timing variation)between the actual valve timing calculated immediately before the enginestopped and the target valve timing is calculated. And in step 2003, thephase variation of the motor 26 since the engine stopped is totaled toobtain an actual phase variation of the motor 26. The phase variation ofthe motor 26 is for example given a plus value in the forward rotationdirection of the motor and a minus value in the reverse rotationdirection of the motor.

After this, in step 2004 and step 2005, the actual phase variation ofthe motor 26 since the engine stopped and the target phase variation arecompared. If the actual phase variation of the motor 26 is lower thanthe target phase variation, the motor 26 is controlled to rotate forwardin step 2006, and if the actual phase variation of the motor 26 isgreater than the target phase variation the motor 26 is controlled torotate backward in step 2007.

After that, when in step 2004 it is determined that the actual phasevariation of the motor 26 since the motor stopped matches the targetphase variation, in step 2008 it is determined that the actual valvetiming of the stopped engine (the actual valve timing of immediatelybefore the engine stopped+the valve timing variation) has reached thetarget valve timing. Then, in step 2009, the motor 26 is stopped and theactual valve timing as of that point in time is held.

In this twentieth embodiment also it is possible to calculate the actualvalve timing of the stopped engine indirectly and make this actual valvetiming match a target valve timing, and it is possible to executevariable valve timing control with good accuracy.

(Twenty-first Embodiment)

As in the foregoing seventeenth embodiment and twentieth embodiment, bycontrolling an amount of rotation (number of revolutions, rotationangle, phase variation) of the motor 26 showing an amount of actuationof the variable valve timing device 18 after the engine is stopped, itis possible to make the actual valve timing of the stopped engine matcha target valve timing. However, the amount of actuation of the variablevalve timing device 18 (amount of rotation of the motor 26) discussedabove is not the only parameter expressing the valve timing variationsince the engine stopped, and for example it is also possible to employthe amount of driving force supplied to the variable valve timingdevice.

In a twenty-first embodiment of the invention shown in FIG. 45, inexecuting variable valve timing control while the engine is stopped, asthe amount of driving force supplied to the variable valve timing device18 mentioned above, the amount of electric power supplied to the motor26 of the variable valve timing device 18 is used. That is, an actualamount of electric power supplied to the motor 26 after the engine stopsis controlled so as to match it to a target amount of supplied electricpower to bring the actual valve timing of the stopped engine to a targetvalve timing.

In the twenty-first embodiment, a valve timing control program for whenthe engine is stopped shown in FIG. 45 is executed. When this program isstarted, first, in a step 2101, a target valve timing is calculated.Then, in step 2102, the target amount of the electric power supplied tothe motor 26 corresponding to the difference (target valve timingvariation) between the actual valve timing calculated immediately beforethe engine stopped and the target valve timing is calculated. Afterthat, in step 2103, the amount of the electric power supplied to themotor 26 since the engine stopped is totaled to obtain the actual amountof the electric power supplied to the motor 26. The amount of theelectric power supplied to the motor 26 is for example given a plusvalue in the forward rotation direction of the motor and a minus valuein the reverse rotation direction of the motor.

After this, in step 2104 and step 2105, the actual amount of theelectric power supplied to the motor 26 since the engine stopped and thetarget amount of the supplied electric power are compared. If the actualamount of the electric power supplied to the motor 26 is smaller thanthe target amount of the supplied electric power, in step 2106electrical power in the forward rotation direction is supplied to themotor 26. On the other hand, if the actual amount of the electric powersupplied to the motor 26 is larger than the target amount of thesupplied electric power, in step 2107 electrical power in the reverserotation direction is supplied to the motor 26.

After that, when in step 2104 it is determined that the actual amount ofthe electric power supplied to the motor 26 since the engine stoppedmatches the target amount of the supplied electric power, in step 2108it is determined that the actual valve timing of the stopped engine (theactual valve timing of immediately before the engine stopped+the valvetiming variation) has reached the target valve timing. Then, in step2109, the supply of electrical power to the motor 26 is stopped and theactual valve timing of that point in time is held.

With the twenty-first embodiment described above also, it is possible tocalculate the actual valve timing of the stopped engine indirectly andmake this actual valve timing match a target valve timing, and variablevalve timing control can be executed with good accuracy.

(Twenty-second Embodiment)

In the twenty-first embodiment described above, because the variablevalve timing device 18 was motor-driven, as the amount of driving forceto the variable valve timing device 18 the amount of electric powersupplied to the motor 26 of the variable valve timing device 18 wasused.

In a twenty-second embodiment, in a case where a hydraulically drivenvariable valve timing device is used, the amount of oil supplied from ahydraulic drive source (an electric oil pump) is employed as the amountof driving force supplied to the variable valve timing device. That is,in a twenty-second embodiment of the invention shown in FIG. 46, in ahydraulically driven variable valve timing device (hereinafter,“hydraulic VCT”) driven by hydraulic pressure supplied from an electricoil pump or the like provided separately from the engine 11, an actualamount of oil supplied to the hydraulic VCT since the engine stopped iscontrolled to match a target amount of supplied oil to make the actualvalve timing of the stopped engine match a target valve timing.

In this twenty-second embodiment, a valve timing control program forwhen the engine is stopped shown in FIG. 46 is executed. When thisprogram is started, first, in a step 2201, a target valve timing iscalculated. Then, in a step 2202, a target amount of oil supplied to thehydraulic VCT corresponding to the difference (target valve timingvariation) between the actual valve timing calculated immediately beforethe engine stopped and the target valve timing is calculated. And instep 2203, the amount of oil supplied to the hydraulic VCT since theengine stopped is totaled to obtain the actual amount of oil supplied tothe hydraulic VCT. The amount of oil supplied to the hydraulic VCT isfor example given a plus value in the valve timing advancing directionand a minus value in the valve timing retarding direction.

After this, in step 2204 and step 2205 the actual amount of oil suppliedto the hydraulic VCT since the engine stopped and the target amount ofsupplied oil are compared, and if the actual amount of oil supplied tothe hydraulic VCT is smaller than the target amount of supplied oil, instep 2206 a hydraulic pressure in the valve timing advancing directionis supplied to the hydraulic VCT. On the other hand, if the actualamount of oil supplied to the hydraulic VCT is larger than the targetamount of supplied oil, in step 2207 a hydraulic pressure in the valvetiming retarding direction is supplied to the hydraulic VCT.

After that, when in step 2204 it is determined that the actual amount ofoil supplied to the hydraulic VCT matches the target amount of suppliedoil, in step 2208 it is determined that the actual valve timing of thestopped engine (the actual valve timing of immediately before the enginestopped+the valve timing variation) has reached the target valve timing.Then, in step 2209, the condition of the oil supply to the hydraulic VCTis held to hold the actual valve timing of that point in time.

In the twenty-second embodiment described above also, it is possible tocalculate the actual valve timing of the stopped engine indirectly andmake this actual valve timing match a target valve timing, and variablevalve timing control can be executed with good accuracy.

(Twenty-third Embodiment)

In controlling the actual valve timing to a reference position (mostadvanced angle position or most retarded angle position) when the engineis rotating backward or stopped after rotating backward, in theforegoing seventeenth embodiment, it was determined whether or not theactual valve timing had reached the reference position on the basis ofwhether or not the actual accumulated value of the control output to themotor 26 had risen above a target accumulated value of the controloutput. With respect to this, in a twenty-third embodiment, it isdetermined whether or not the actual valve timing has reached thereference position on the basis of whether or not an actual totalcontrol time value of the motor 26 has risen above a target totalcontrol time value. That is, in determining the control output to thevariable valve timing device 18, besides the accumulated value of thatcontrol output, it is also possible to determine whether or not theactual valve timing has reached the reference position by using a totalvalue of control time.

In the twenty-third embodiment, a reference position arrivaldetermination program shown in FIG. 47 is executed. In this program,first, in a step 2301, a target total control time value of the motor 26needed to bring the actual valve timing to the reference position (amost advanced angle position or a most retarded angle position) (to makethe moving part of the phase-varying mechanism 21 hit the stopper part)is calculated. After that, processing proceeds to step 2302, and totalsthe motor control time from when the motor 26 started to be controlledto move the actual valve timing in the direction of the referenceposition (most advanced angle position or most retarded angle position)to obtain an actual total control time value.

After this, in step 2303, the actual total control time value of themotor 26 and the target total control time value are compared. When theactual total control time value of the motor 26 has risen above thetarget total control time value, in step 2304 it is deduced that theactual valve timing has arrived at the reference position (most advancedangle position or most retarded angle position).

With this twenty-third embodiment also, it is possible to determineaccurately whether or not the actual valve timing has reached thereference position (most advanced angle position or most retarded angleposition).

(Twenty-fourth Embodiment)

In the foregoing seventeenth to twenty-third embodiments, it wasdetermined whether or not the actual valve timing had reached areference position on the basis of a control output to the variablevalve timing device 18. However, whether or not the actual valve timinghas reached a reference position can also be determined on the basis ofan operating state of the variable valve timing device 18.

A twenty-fourth embodiment shown in FIG. 48 focuses on the fact thatwhen the actual valve timing reaches the reference position (mostadvanced angle position or most retarded angle position) and the movingpart of the phase-varying mechanism 21 hits the stopper part, therotation of the motor 26 slows suddenly to the same speed as thecamshaft speed or stops suddenly, and the current value or voltage valueof the motor 26 increases. That is, in this embodiment, as an operatingstate of the variable valve timing device 18, the actual current valueor actual voltage value of the motor 26 is monitored, and whether or notthe actual valve timing has reached the reference position is determinedon the basis of whether or not the actual current value or actualvoltage value has risen above a predetermined threshold value.

In the twenty-fourth embodiment, a reference position arrivaldetermination program shown in FIG. 48 is executed. In this program,first, in a step 2401, a motor current threshold value or a motorvoltage threshold value for determining whether or not the actual valvetiming has reached the reference position (most advanced angle positionor most retarded angle position) (that is, whether or not the rotationof the motor 26 is being restricted and consequently the current valueor the voltage value of the motor 26 has increased) is calculated. Afterthat, in step 2402, the actual current value or the actual voltage valueof the motor 26 is detected.

After this, in step 2403, the actual current value (or actual voltagevalue) of the motor 26 and the motor current threshold value (or motorvoltage threshold value) are compared. When the actual current value (oractual voltage value) of the motor 26 has risen above the motor currentthreshold value (or motor voltage threshold value), in step 2404, it isinferred that the actual valve timing has reached the reference position(most advanced angle position or most retarded angle position).

With this twenty-third embodiment also, it is possible to determineaccurately whether or not the actual valve timing has reached thereference position (most advanced angle position or most retarded angleposition).

(Twenty-fifth Embodiment)

The twenty-fifth embodiment constitutes a variation of the twenty-fourthembodiment described above. That is, in this twenty-fifth embodiment,when the actual valve timing reaches the reference position (mostadvanced angle position or most retarded angle position) and the movingpart of the phase-varying mechanism 21 hits the stopper part and therotation of the motor 26 slows suddenly to the same speed as thecamshaft speed or stops suddenly, this is detected on the basis of theactual speed of the motor 26. Specifically, when the rotation of themotor 26 slows suddenly to the same speed as the camshaft speed or stopssuddenly and the actual speed of the motor 26 falls below apredetermined threshold value, it is determined that the actual valvetiming has arrived at the reference position.

In the twenty-fifth embodiment, the reference position arrivaldetermination program shown in FIG. 49 is executed. In this program,first, in a step 2501, a motor speed threshold value for determiningwhether or not the actual valve timing has reached the referenceposition (most advanced angle position or most retarded angle position)(that is, whether or not the speed of the motor 26 has fallen suddenly)is calculated. After that, in step 2502, the actual speed of the motor26 is detected.

After this, in step 2503, the actual speed of the motor 26 and the motorspeed threshold value are compared. When the actual speed of the motor26 has fallen below the motor speed threshold value, in step 2504, it isinferred that the actual valve timing has arrived at the referenceposition (most advanced angle position or most retarded angle position).

With this twenty-fifth embodiment also, it is possible to determineaccurately whether or not the actual valve timing has reached thereference position (most advanced angle position or most retarded angleposition).

(Twenty-sixth Embodiment)

Next, a twenty-sixth embodiment of the invention will be described,using FIG. 50.

When the engine speed is low, such as on starting and stopping of theengine, the generated power (battery charging power) of an alternatordriven by the engine 11 falls, and the battery voltage tends to fall.When during variable valve timing control on starting or stopping of theengine the battery voltage becomes too low, there is a possibility ofthe power supplied to the variable valve timing device 18 becominginsufficient and deficient operation of the variable valve timing device18 occurring or of the power supplied to the starter becominginsufficient and the startability of the engine 11 falling.

As a countermeasure to this, in a twenty-sixth embodiment, by anoperating condition alteration program of the variable valve timingdevice shown in FIG. 50 being executed, when the engine speed is lowerthan a predetermined value, an operating condition of the variable valvetiming device 18 is changed in correspondence with the battery voltage.By this means, even when the battery voltage falls when the engine speedfalls at times such as on starting and stopping of the engine, anoperating condition of the variable valve timing device 18 can bechanged so that the variable valve timing device 18 can operate normallyunder that battery voltage condition or so that the power supply to thestarter can be secured.

The operating condition alteration program of the variable valve timingdevice 18 shown in FIG. 50 is executed with a predetermined period overthe time from when the IG switch is turned on to when the VCT driverelay is turned off. When this program is started, first, in a step2601, the present battery voltage is detected. After that, in step 2602,the present engine speed is detected. Then, in step 2603, it isdetermined whether or not the engine speed is above a predeterminedvalue. This predetermined value is set to an engine speed such that itis possible to secure a sufficient generated power (battery chargingpower) of an alternator driven by the engine 11. If as the result it isdetermined that the engine speed is above the predetermined value, it isinferred that problems caused by battery voltage drop will not occur,and the present program ends.

When on the other hand in step 2603 it is determined that the enginespeed is lower than the predetermined value, processing proceeds to step2604 and determines whether or not the battery voltage is above a firstpredetermined value V1. If as the result it is determined that thebattery voltage is above the first predetermined value V1, it isinferred that problems caused by battery voltage drop will not occur,and the present program ends.

When in step 2604 it is determined that the battery voltage is lowerthan the first predetermined value V1, processing proceeds to step 2605and determines whether or not the battery voltage is above a secondpredetermined value V2. This second predetermined value V2 is set to alower voltage value than the first predetermined value V1. When as theresult it is determined that the battery voltage is lower than the firstpredetermined value V1 and higher than the second predetermined valueV2, processing proceeds to step 2606 and limits an actuation speed ofthe variable valve timing device 18 to below a predetermined speed andthereby reduces the power consumption of the variable valve timingdevice 18. By this means, the variable valve timing device 18 isoperated normally in a low-power-consumption mode, and power supply tothe starter and so on is ensured.

With respect to this, when it is determined that the battery voltage islower than the second predetermined value V1, it is determined that thiscannot be dealt with by an operation speed limiting on the variablevalve timing device 18, and processing proceeds to step 2607 andprohibits operation of the variable valve timing device 18. By thismeans, defective operation of the variable valve timing device 18 anddeficient power supply to the starter can be certainly prevented.

With the twenty-sixth embodiment described above, when the engine speedis lower than a predetermined value, in correspondence with the batteryvoltage the actuation speed of the variable valve timing device 18 islimited or operation of the variable valve timing device 18 isprohibited. As a result, even when a fall in the battery voltage occurson starting or stopping of the engine, defective operation of thevariable valve timing device 18 and deterioration of the startability ofthe engine arising due to this voltage fall can be prevented, and thequality of control on starting and stopping of the engine can beincreased.

The predetermined value (threshold value) of the engine speed and thepredetermined value (threshold value) of the battery voltage in thetwenty-sixth embodiment may be altered in accordance with the enginestate (temperature, engine load, electric load, oil viscosity and soon). If this is done, as times when the battery load is large, such asfor example on cold-starting, the predetermined value of the enginespeed or the predetermined value of the battery voltage can be madelarge to prevent problems caused by battery voltage deficiency.

And, although in the twenty-sixth embodiment the actuation speed of thevariable valve timing device 18 was limited when the battery voltage waslow, some other operating condition of the variable valve timing device18 (for example an amount of operation) may alternatively be altered.

And although the twenty-sixth embodiment may be implemented incombination with the other embodiments described above, it may also beimplemented alone.

And although in the foregoing seventeenth embodiment to twenty-sixthembodiment reverse rotation of the engine was determined on the valvetiming control program side, alternatively reverse rotation of theengine may be determined on the engine control program side, and thisdetermination result used in the valve timing control program. And thedetermination result of an engine reverse rotation determinationexecuted on the valve timing control program side may be reflected onthe engine control program side, and for example fuel-cutting control onreverse rotation determination may be executed.

And, in the foregoing seventeenth embodiment to twenty-sixth embodiment,in the executing of variable valve timing control with the enginestopped, by controlling a parameter expressing valve timing variationsuch as the amount of rotation of the motor 26 (number of revolutions,phase variation) since the engine stopped to a target value, the actualvalve timing of the stopped engine was made to match a target valvetiming without the actual valve timing being directly calculated whilethe engine is stopped. However, alternatively the actual valve timing ofthe stopped engine (actual valve timing immediately before the enginestopped+valve timing variation) can be calculated on the basis of theactual valve timing immediately before the engine stopped and aparameter expressing a valve timing variation such as the amount ofrotation (number of revolutions, phase variation) of the motor 26, andthe variable valve timing device 18 may be feedback-controlled so as tomake the actual valve timing of the stopped engine match a target valvetiming.

And, the invention is not limited to a variable valve timing controldevice for intake valves as in the foregoing seventeenth embodiment totwenty-sixth embodiment, and may alternatively be applied to a variablevalve timing control device for exhaust valves Also, the construction ofthe variable valve timing device 18 may be suitably modified, and inshort it may be any variable valve timing device driven by a drivesource such as a motor or an oil pump provided separately from theengine.

1. A variable valve timing control device of an internal combustionengine for controlling a variable valve timing device which varies valvetiming of intake valves or exhaust valves driven to open and close by acamshaft by varying a rotation phase of the camshaft (hereinafter,referred to as “camshaft phase”) with respect to a crankshaft of theinternal combustion engine, said variable valve timing devicecomprising: a first rotating member disposed concentrically with saidcamshaft and rotationally driven by rotary drive power from saidcrankshaft; a second rotating member that rotates integrally with saidcamshaft; a phase-varying member that transmits rotary power from saidfirst rotating member to said second rotating member and varies rotationphase of said second rotating member with respect to said first rotatingmember; and a motor disposed concentrically with said camshaft so as tocontrol the rotation phase of this phase-varying member, wherein saidvariable valve timing device is constructed so that when said valvetiming is not to be changed a speed of said motor is matched to a speedof said camshaft to match a turning speed of said phase-varying memberto the speed of said camshaft and thereby hold a difference in rotationphase between said first rotating member and said second rotating membersteady and thus hold said camshaft phase steady, and when said valvetiming is to be changed the speed of said motor is changed with respectto the speed of said camshaft to change the turning speed of saidphase-varying member with respect to the speed of said camshaft andthereby vary the difference in rotation phase between said firstrotating member and said second rotating member and thus vary saidcamshaft phase, said variable valve timing control device comprising:required valve timing change rate calculating means for calculating arequired valve timing change rate on a basis of a deviation between atarget valve timing and an actual valve timing; required speeddifference calculating means for calculating a required speed differencebetween said motor and said camshaft on a basis of said required valvetiming change rate; and motor control value calculating means forcalculating a motor control value so as to control a speed differencebetween said motor and said camshaft to said required speed difference.2. A variable valve timing control device of an internal combustionengine according to claim 1, wherein said motor control valuecalculating means calculates a required motor speed on a basis of thespeed of said camshaft and said required speed difference, and saidmotor control value so as to control the speed of said motor to saidrequired motor speed.
 3. A variable valve timing control device of aninternal combustion engine according to claim 1, wherein said motorcontrol value calculating means calculates a basic control value forcontrolling the speed of said motor to a basic motor speed identicalwith the speed of said camshaft, a change control value for changing thespeed of said motor by said required speed difference with respect tosaid basic motor speed, and said motor control value on a basis of saidbasic control value and change control value.
 4. A variable valve timingcontrol device of an internal combustion engine according to claim 1,wherein said motor control value calculating means calculates said motorcontrol value so as to control the speed of said motor to the same speedas the speed of said camshaft, when the deviation between the targetvalve timing and the actual valve timing is below a predetermined value.5. A variable valve timing control device of an internal combustionengine according to claim 1, wherein said motor control valuecalculating means calculates said motor control value using at least oneamong a frictional loss in said variable valve timing device or aparameter correlated therewith a drive loss on a camshaft side or aparameter correlated therewith, and a counter-electromotive force ofsaid motor or a parameter correlated therewith.
 6. A variable valvetiming control device of an internal combustion engine according toclaim 5, wherein said motor control value calculating means calculates,in correspondence with said required speed difference, the frictionalloss in said variable valve timing device or the parameter correlatedtherewith.
 7. A variable valve timing control device of an internalcombustion engine according to claim 5, wherein said motor control valuecalculating means calculates, in correspondence with said required motorspeed calculated on a basis of the speed of said camshaft and saidrequired speed difference, the counter-electromotive force of said motoror the parameter correlated therewith.
 8. A variable valve timingcontrol device of an internal combustion engine according to claim 1,wherein said motor control value calculating means corrects said motorcontrol value on a basis of the speed of said motor and/or whether it isincreasing or decreasing.
 9. A variable valve timing control device ofan internal combustion engine according to claim 8, wherein said motorcontrol value calculating means calculates a duty value forduty-controlling power supplied to said motor as said motor controlvalue.
 10. A variable valve timing control device of an internalcombustion engine according to claim 1, wherein a limit value is set onat least one among said valve timing change rate, the speed differencebetween said motor and camshaft, and the speed of said motor.
 11. Amotor-driven variable valve timing control device of an internalcombustion engine, which changes a camshaft phase by adjusting a speedof a motor with respect to a speed of a camshaft, comprising; requiredvalve timing change rate calculating means for calculating a requiredvalve timing change rate on a basis of a deviation between a targetvalve timing and an actual valve timing; required speed differencecalculating means for calculating a required speed difference betweensaid motor and said camshaft on a basis of said required valve timingchange rate; and motor control value calculating means for calculating amotor control value so as to control a speed difference between saidmotor and said camshaft to said required speed difference.
 12. Amotor-driven variable valve timing control device of an internalcombustion engine according to claim 11, wherein said motor controlvalue calculating means calculates a required motor speed on a basis ofthe speed of said camshaft and said required speed difference, and saidmotor control value so as to control the speed of said motor to saidrequired motor speed.
 13. A motor-driven variable valve timing controldevice of an internal combustion engine according to claim 11, whereinsaid motor control value calculating means calculates a basic controlvalue for controlling the speed of said motor to a basic motor speedidentical with the speed of said camshaft, a change control value forchanging the speed of said motor by said required speed difference withrespect to said basic motor speed, and said motor control value on abasis of said basic control value and change control value.
 14. Amotor-driven variable valve timing control device of an internalcombustion engine according to a claim 11, wherein said motor controlvalue calculating means calculates said motor control value so as tocontrol the speed of said motor to the same speed as the speed of saidcamshaft, when the deviation between the target valve timing and theactual valve timing is below a predetermined value.
 15. A motor-drivenvariable valve timing control device of an internal combustion engineaccording to claim 11, wherein said motor control value calculatingmeans calculates said motor control value using at least one among africtional loss in said variable valve timing device or a parametercorrelated therewith, a drive loss on a camshaft side or a parametercorrelated therewith, and a counter-electromotive force of said motor ora parameter correlated therewith.
 16. A motor-driven variable valvetiming control device of an internal combustion engine according toclaim 15, wherein said motor control value calculating means calculates,in correspondence with said required speed difference, the frictionalloss in said variable valve timing device or the parameter correlatedtherewith.
 17. A motor-driven variable valve timing control device of aninternal combustion engine according to claim 15, wherein said motorcontrol value calculating means calculates, in correspondence with saidrequired motor speed calculated on a basis of the speed of said camshaftand said required speed difference, the counter-electromotive force ofsaid motor or the parameter correlated therewith.
 18. A motor-drivenvariable valve timing control device of an internal combustion engineaccording to claim 11, wherein said motor control value calculatingmeans corrects said motor control value on a basis of the speed of saidmotor and/or whether it is increasing or decreasing.
 19. A motor-drivenvariable valve timing control device of an internal combustion engineaccording to claim 18, wherein said motor control value calculatingmeans calculates a duty value for duty-controlling power supplied tosaid motor as said motor control value.
 20. A motor-driven variablevalve timing control device of an internal combustion engine accordingto claim 11, wherein a limit value is set on at least one among saidvalve timing change rate, the speed difference between said motor andcamshaft, and the speed of said motor.
 21. A variable valve timingcontrol device of an internal combustion engine for controlling avariable valve timing device which varies valve timing of intake valvesor exhaust valves driven to open and close by a camshaft by varying arotation phase of the camshaft (hereinafter, referred to as “camshaftphase”) with respect to a crankshaft of the internal combustion engine,said variable valve timing device comprising: a first rotating memberdisposed concentrically with said camshaft and rotationally driven byrotary drive power from said crankshaft; a second rotating member thatrotates integrally with said camshaft; a phase-varying member thattransmits rotary power from said first rotating member to said secondrotating member and varies rotation phase of said second rotating memberwith respect to said first rotating member; and a motor disposedconcentrically with said camshaft so as to control the rotation phase ofthis phase-varying member, wherein said variable valve timing device isconstructed so that when said valve timing is not to be changed a speedof said motor is matched to a speed of said camshaft to match a turningspeed of said phase-varying member to the speed of said camshaft andthereby hold a difference in rotation phase between said first rotatingmember and said second rotating member steady and thus hold saidcamshaft phase steady, and when said valve timing is to be changed thespeed of said motor is changed with respect to the speed of saidcamshaft to change the turning speed of said phase-varying member withrespect to the speed of said camshaft and thereby vary the difference inrotation phase between said first rotating member and said secondrotating member and thus vary said camshaft phase, said variable valvetiming control device comprising: a crank angle sensor for outputting acrank angle signal at intervals of a predetermined crank angle; a camangle sensor for outputting a cam angle signal at intervals of apredetermined cam angle; cam angle signal output time valve timingcalculating means for calculating, every time said cam angle signal isoutputted, an actual valve timing at the time of outputting of the camangle signal on a basis of the cam angle signal and the crank anglesignal; valve timing variation calculating means for calculating a valvetiming variation with a predetermined computation period on a basis of adifference between the speed of said motor and the speed of saidcamshaft; final valve timing calculating means for calculating a finalactual valve timing with a predetermined computation period on a basisof a calculated value of the actual valve timing at the time ofoutputting of said cam angle signal and a calculated value of the valvetiming variation.
 22. A variable valve timing control device of aninternal combustion engine according to claim 21, wherein said valvetiming variation calculating means has means for calculating a valvetiming variation per computation period and accumulating the calculatedvalues, and means for resetting an accumulated value of the valve timingvariation every time said cam angle signal is outputted, and whereinsaid final valve timing calculating means calculates the final actualvalve timing by adding to the calculated value of the actual valvetiming at a time of the most recent outputting of the cam angle signalthe accumulated value of subsequent valve timing variation.
 23. Avariable valve timing control device of an internal combustion engineaccording to claim 21, wherein said valve timing variation calculatingmeans uses a ½ value of a speed of said crankshaft detected on a basisof an output period of the crank angle signal of said crank angle sensoras a speed data of said camshaft.
 24. A variable valve timing controldevice of an internal combustion engine according to claim 21, whereinsaid final valve timing calculating means calculates the final actualvalve timing by adding to the calculated value of the actual valvetiming of when the internal combustion engine stops an accumulated valueof subsequent valve timing variation, or with an accumulated value ofvalve timing variation from a reference position, while the internalcombustion engine is stopped.
 25. A variable valve timing control deviceof an internal combustion engine according to claim 21, wherein saidfinal valve timing calculating means calculates the final actual valvetiming by adding to the calculated value of the actual valve timing at atime of a last outputting of the cam angle signal before a failure anaccumulated value of subsequent valve timing variation, or with anaccumulated value of valve timing variation from a reference position,when said cam angle sensor fails.
 26. A motor-driven variable valvetiming control device of an internal combustion engine, which changes acamshaft phase by adjusting a speed of a motor with respect to a speedof a camshaft, comprising; a crank angle sensor for outputting a crankangle signal at intervals of a predetermined crank angle; a cam anglesensor for outputting a cam angle signal at intervals of a predeterminedcam angle; cam angle signal output time valve timing calculating meansfor calculating, every time said cam angle signal is outputted, anactual valve timing at the time of outputting of the cam angle signal ona basis of the cam angle signal and the crank angle signal; valve timingvariation calculating means for calculating a valve timing variationwith a predetermined computation period on a basis of a differencebetween the speed of said motor and the speed of said camshaft; finalvalve timing calculating means for calculating a final actual valvetiming with a predetermined computation period on a basis of acalculated value of the actual valve timing at the time of outputting ofsaid cam angle signal and a calculated value of the valve timingvariation.
 27. A variable valve timing control device of an internalcombustion engine according to claim 26, wherein said valve timingvariation calculating means has means for calculating a valve timingvariation per computation period and accumulating the calculated values,and means for resetting an accumulated value of the valve timingvariation every time said cam angle signal is outputted, and whereinsaid final valve timing calculating means calculates the final actualvalve timing by adding to the calculated value of the actual valvetiming at a time of the most recent outputting of the cam angle signalthe accumulated value of subsequent valve timing variation.
 28. Avariable valve timing control device of an internal combustion engineaccording to claim 26, wherein said valve timing variation calculatingmeans uses a ½ value of a speed of said crankshaft detected on a basisof an output period of the crank angle signal of said crank angle sensoras a speed data of said camshaft.
 29. A variable valve timing controldevice of an internal combustion engine according to claim 26, whereinsaid final valve timing calculating means calculates the final actualvalve timing by adding to the calculated value of the actual valvetiming of when the internal combustion engine stops an accumulated valueof subsequent valve timing variation, or with an accumulated value ofvalve timing variation from a reference position, while the internalcombustion engine is stopped.
 30. A variable valve timing control deviceof an internal combustion engine according claim 26, wherein said finalvalve timing calculating means calculates the final actual valve timingby adding to the calculated value of the actual valve timing at a timeof a last outputting of the cam angle signal before a failure anaccumulated value of subsequent valve timing variation, or with anaccumulated value of valve timing variation from a reference position,when said cam angle sensor fails.
 31. A motor-driven variable valvetiming control device of an internal combustion engine, which changes acamshaft phase by adjusting a speed of a motor with respect to a speedof a camshaft, comprising; a crank angle sensor for outputting a crankangle signal at intervals of a predetermined crank angle; a cam anglesensor for outputting a cam angle signal at intervals of a predeterminedcam angle; a motor angle sensor for outputting a motor angle signal atintervals of a predetermined motor angle; means for calculating avariation of a motor rotation angle; means for calculating a variationof a camshaft rotation angle; cam angle signal output time valve timingcalculating means for calculating, every time said cam angle signal isoutputted, an actual valve timing at a time of outputting of the camangle signal on a basis of the cam angle signal and the crank anglesignal; valve timing variation calculating means for calculating a valvetiming variation on a basis of a difference between the variation of themotor rotation angle and the variation of the camshaft rotation angle;final valve timing calculating means for calculating a final actualvalve timing on a basis of a calculated value of the actual valve timingat the time of outputting of said cam angle signal and a calculatedvalue of the valve timing variation.
 32. A variable valve timing controldevice of an internal combustion engine according to claim 31, whereinsaid valve timing variation calculating means has means for calculatinga valve timing variation per computation period and accumulating thecalculated values, and means for resetting an accumulated value of thevalve timing variation every time said cam angle signal is outputted,and wherein said final valve timing calculating means calculates thefinal actual valve timing by adding to the calculated value of theactual valve timing at a time of the most recent outputting of the camangle signal the accumulated value of subsequent valve timing variation.33. A variable valve timing control device of an internal combustionengine according to claim 31, wherein the variation of the motorrotation angle is calculated from a variation of a motor angle counterwhich counts based on a number of outputting of the motor angle sensorfor outputting the motor angle signal at intervals of the predeterminedmotor angle.
 34. A variable valve timing control device of an internalcombustion engine according to claim 31, wherein the variation of thecamshaft rotation angle is a ½ value of a crank angle variationcalculated from a variation of a crank angle counter which counts basedon a number of outputting of the crank angle sensor for outputting thecrank angle signal at intervals of the predetermined crank angle.
 35. Avariable valve timing control device of an internal combustion engineaccording to claim 31, wherein said final valve timing calculating meanscalculates the final actual valve timing by adding to the calculatedvalue of the actual valve timing of when the internal combustion enginestops an accumulated value of subsequent valve timing variation, or withan accumulated value of valve timing variation from a referenceposition, while the internal combustion engine is stopped.
 36. Avariable valve timing control device of an internal combustion engineaccording to claim 31, wherein said final valve timing calculating meanscalculates the final actual valve timing by adding to the calculatedvalue of the actual valve timing at a time of a last outputting of thecam angle signal before a failure an accumulated value of subsequentvalve timing variation, or with an accumulated value of valve timingvariation from a reference position, when said cam angle sensor fails.37. A variable valve timing control device of an internal combustionengine, comprising: a variable valve timing device which varies valvetiming of intake valves or exhaust valves of the internal combustionengine with a gear mechanism; and control means for controlling thevariable valve timing device, wherein said control means executesrate-limiting control for limiting a valve timing change rate to apredetermined rate or less, when an actual valve timing is in apredetermined rate-limited region set in a vicinity of a limit positionof a movable range of the variable valve timing device.
 38. A variablevalve timing control device of an internal combustion engine accordingto claim 37, wherein said control means does not execute therate-limiting control when the actual valve timing is being changed inan opposite direction from a limit position of the rate-limited regioneven though the actual valve timing is in the rate-limited region.
 39. Avariable valve timing control device of an internal combustion engineaccording to claim 37, wherein said rate-limiting region is set on abasis of a valve timing variation needed to slow the valve timing changerate to the predetermined rate and/or on an actual valve timingdetection error.
 40. A variable valve timing control device of aninternal combustion engine according to claim 37, further comprising:reference position learning means for learning a reference position ofthe valve timing, wherein said control means executes rate-limitingcontrol for limiting the valve timing change rate to the predeterminedrate or less, when said reference position learning means has notcompleted learning of the reference position.
 41. A variable valvetiming control device of an internal combustion engine, comprising: avariable valve timing device which varies valve timing of intake valvesor exhaust valves of the internal combustion engine with a gearmechanism; control means for controlling the variable valve timingdevice; and reference position learning means for learning a referenceposition of the valve timing, wherein said control means executesrate-limiting control for limiting a valve timing change rate to apredetermined rate or less, when said reference position learning meanshas not completed learning of the reference position.
 42. A variablevalve timing control device of an internal combustion engine accordingto claim 40, wherein said control means executes said rate-limitingcontrol in a region where a difference between an actual valve timingand a limit position of a movable range of said variable valve timingdevice is within a predetermined value, when said reference positionlearning means has not completed learning of the reference position. 43.A variable valve timing control device of an internal combustion engineaccording to claim 40, wherein said control means sets a target valvetiming in accordance with the valve timing change rate limited to thepredetermined rate or less by said rate-limiting control, when executingvariable valve timing control in a state that said reference positionlearning means has not completed learning of the reference position. 44.A variable valve timing control device of an internal combustion engineaccording to claim 40, wherein said reference position learning meansprohibits normal variable valve timing control until reference positionlearning has been completed and executes only reference positionlearning.
 45. A variable valve timing control device of an internalcombustion engine, comprising: a variable valve timing device whichvaries valve timing of intake valves or exhaust valves of the internalcombustion engine with a gear mechanism; control means for controllingthe variable valve timing device; reference position learning means forlearning a reference position of the valve timing; and learningabnormality determination means for determining whether or not there hasbeen an abnormality in reference position learning executed by saidreference position learning means, wherein said control means executesrate-limiting control for limiting a valve timing change rate to apredetermined rate or less, when said learning abnormality determinationmeans determines that there has been an abnormality in referenceposition learning.
 46. A variable valve timing control device of aninternal combustion engine according to claim 45, wherein said learningabnormality determination means determines that there has been anabnormality in reference position learning, when a reference positionlearning value of said reference position learning means exceeds apredetermined guard value.
 47. A variable valve timing control device ofan internal combustion engine according to claim 45, wherein saidcontrol means sets a target valve timing in accordance with the valvetiming change rate limited to the predetermined rate or less by saidrate-limiting control, when executing variable valve timing control in astate that said learning abnormality determination means determines thatthere has been an abnormality in reference position learning.
 48. Avariable valve timing control device of an internal combustion engineaccording to claim 45, wherein said control means prohibits normalvariable valve timing control and executes only reference positionlearning until said learning abnormality determination means determinesthat there is no abnormality in reference position learning.
 49. Avariable valve timing control device of an internal combustion engineaccording to claim 40, wherein said reference position leaning meanslearns the reference position before the internal combustion engine isstarted.
 50. A variable valve timing control device of an internalcombustion engine according to claim 49, further comprising startprohibiting means for prohibiting start control of said internalcombustion engine until said reference position learning has beencompleted.
 51. A variable valve timing control device of an internalcombustion engine according to claim 50, wherein said start prohibitingmeans limits execution of a processing for prohibiting start control ofsaid internal combustion engine until said reference position learninghas been completed to a predetermined time from when an ignition switchis turned on.
 52. A variable valve timing control device of an internalcombustion engine according to claim 37, wherein said gear mechanismcomprising: a first rotating member disposed concentrically with acamshaft and rotationally driven by rotary drive power from acrankshaft; a second rotating member that rotates integrally with saidcamshaft; and a phase-varying member that transmits rotary power fromsaid first rotating member to said second rotating member and variesrotation phase of said second rotating member with respect to said firstrotating member, and wherein drive power transmitting means between saidfirst rotating member and said phase-varying member and/or drive powertransmitting means between said second rotating member and saidphase-varying member is constructed by a gear wheel, and furthercomprising a motor for controlling a rotation phase of saidphase-varying member, and wherein said control means, when said valvetiming is not to be changed, matches a speed of said motor to a speed ofsaid camshaft to match a turning speed of said phase-varying member tothe speed of said camshaft and thereby hold a difference in rotationphase between said first rotating member and said second rotating membersteady and thus hold said valve timing steady, and when said valvetiming is to be changed, changes the speed of said motor with respect tothe speed of said camshaft to change the turning speed of saidphase-varying member with respect to the speed of said camshaft andthereby vary the difference in rotation phase between said firstrotating member and said second rotating member and thus vary said valvetiming.
 53. A variable valve timing control device of an internalcombustion engine, comprising: a variable valve timing device forvarying valve timing of intake valves or exhaust valves by means of adrive source provided separately from the internal combustion engine;valve timing control means for controlling the variable valve timingdevice so that an actual valve timing is matched to a target valvetiming (hereinafter, referred to as “variable valve timing control”);and rotation state determination means for determining a rotation stateof the internal combustion engine, wherein said valve timing controlmeans performs actual valve timing calculation and/or variable valvetiming control when said rotation state determination means determinesthat the internal combustion engine is rotating forward or is stopped.54. A variable valve timing control device of an internal combustionengine according to claim 53, wherein said rotation state determinationmeans determines the rotation state of the internal combustion engine ona basis of an output signal from a crank angle sensor and/or a cam anglesensor.
 55. A variable valve timing control device of an internalcombustion engine according to claim 53, wherein said rotation statedetermination means determines that the internal combustion engine isrotating forward when the internal combustion engine is rotating and itis determined that an engine speed at a time when a starter is beingturned on or when the starter is turned off is not less than apredetermined value.
 56. A variable valve timing control device of aninternal combustion engine according to claim 53, further comprising adrive motor having a rotating shaft synchronously rotating with saidcamshaft, wherein said rotation state determination means determines therotation state of the internal combustion engine based on a rotationstate of the motor.
 57. A variable valve timing control device of aninternal combustion engine according to claim 56, wherein said rotationstate determination means determines that the internal combustion engineis rotating forward when a state determined that the internal combustionengine is rotating forward based on the rotation state of the motorafter the starter is turned off is continued for a predetermined time.58. A variable valve timing control device of an internal combustionengine according to claim 56, wherein said variable valve timing devicecomprising: a first rotating member disposed concentrically with thecamshaft and rotationally driven by rotary drive power from acrankshaft; a second rotating member that rotates integrally with thecamshaft; a phase-varying member that transmits rotary power from saidfirst rotating member to said second rotating member and varies rotationphase of said second rotating member with respect to said first rotatingmember; and a motor disposed concentrically with said camshaft so as tocontrol the rotation phase of this phase-varying member, wherein saidvariable valve timing device is constructed so that when said valvetiming is not to be changed a speed of said motor is matched to a speedof said camshaft to match a turning speed of said phase-varying memberto the speed of said camshaft and thereby hold a difference in rotationphase between said first rotating member and said second rotating membersteady and thus hold said valve timing steady, and when said valvetiming is to be changed the speed of said motor is changed with respectto the speed of said camshaft to change the turning speed of saidphase-varying member with respect to the speed of said camshaft andthereby vary the difference in rotation phase between said firstrotating member and said second rotating member and thus vary said valvetiming, and wherein said rotation state determination means determinesthe rotation state of the internal combustion engine based on therotation state of the motor when said variable valve timing device holdsthe valve timing steady.
 59. A variable valve timing control device ofan internal combustion engine according to claim 53, wherein said valvetiming control means controls an actuation amount of said variable valvetiming device and/or a drive power amount supplied to said variablevalve timing device after the engine is stopped to make the actual valvetiming match the target valve timing, when said variable valve timingcontrol is executed while the internal combustion engine is stopped. 60.A variable valve timing control device of an internal combustion engineaccording to claim 59, wherein in a case where said variable valvetiming device is of a type driven by a motor said valve timing controlmeans controls a rotation amount of said motor as the actuation amountof said variable valve timing device.
 61. A variable valve timingcontrol device of an internal combustion engine according to claim 59,wherein in a case where said variable valve timing device is of a typedriven by a motor said valve timing control means controls a suppliedelectric power amount as the drive power amount supplied to saidvariable valve timing device.
 62. A variable valve timing control deviceof an internal combustion engine according to claim 59, wherein in acase where said variable valve timing device is of a type driven by ahydraulic pressure said valve timing control means controls a suppliedoil amount as the drive power amount supplied to said variable valvetiming device.
 63. A variable valve timing control device of an internalcombustion engine according to claim 53, wherein said valve timingcontrol means controls said valve timing to a reference position whensaid rotation state determination means determines a reverse rotation ofthe internal combustion engine.
 64. A variable valve timing controldevice of an internal combustion engine according to claim 63, whereinin a case where said reference position is set to a limit position of amovable range of said variable valve timing device said valve timingcontrol means controls said valve timing to said reference positionwhile the internal combustion engine is rotating backward or while theinternal combustion engine is stopped after rotating backward.
 65. Avariable valve timing control device of an internal combustion engineaccording to claim 64, wherein said valve timing control meansdetermines on a basis of a control output to said variable valve timingdevice whether or not the actual valve timing reaches the referenceposition set to the limit position of the movable range of said variablevalve timing device.
 66. A variable valve timing control device of aninternal combustion engine according to claim 64, wherein said valvetiming control means determines on a basis of an operating state of saidvariable valve timing device whether or not the actual valve timingreaches the reference position set to the limit position of the movablerange of said variable valve timing device.
 67. A variable valve timingcontrol device of an internal combustion engine according to claim 63,wherein in a case where said reference position is set to anintermediate position in a movable range said valve timing control meanscontrols the actual valve timing to said reference position while theinternal combustion engine is stopped after rotating backward.
 68. Avariable valve timing control device of an internal combustion engineaccording to claim 53, wherein said valve timing control means changesan operating condition of said variable valve timing device incorrespondence with a battery voltage when a speed of the internalcombustion engine is lower than a predetermined value.
 69. A variablevalve timing control device of an internal combustion engine,comprising: a variable valve timing device for varying valve timing ofintake valves or exhaust valves by means of a drive source providedseparately from the internal combustion engine; and valve timing controlmeans for controlling the variable valve timing device wherein saidvalve timing control means changes an operating condition of saidvariable valve timing device in correspondence with a battery voltagewhen a speed of the internal combustion engine is lower than apredetermined value.
 70. A variable valve timing control device of aninternal combustion engine according to claim 68, wherein said valvetiming control means limits an actuation speed of said variable valvetiming device when said battery voltage is within a range from a firstpredetermined value to a second predetermined value lower than that, andprohibits an operation of said variable valve timing device when thebattery voltage is lower than said second predetermined value.